Dust.js as a React Delivery Vehicle


Even people in love with Single Page Apps and pooh-poohing server side rendering know that SPAs cannot just materialize in the browser. Something has to deliver them there. Until recently, AngularJS was the most popular client side JS framework, and I have seen all kinds of ADVs (Angular Delivery Vehicles) – from Node.js (N is for Node.js in the MEAN stack), to wonderfully ironic JSP files serving Angular. Particularly exuberant developers go all the way to using static HTML to launch their apps into orbit, extolling the virtues of CDNs.

Of course, I would like to see their faces the first time they realize the need to compute something dynamically in those static files. But that is beside the point. The important takeaway is that AngularJS has a very nice property of being embeddable. You don’t need to surrender your entire page to Angular – you can sequester it to a DIV (in fact, you can have multiple Angular apps running in the same page). This is a very nice feature, but also a necessary one – again, AngularJS is a pure client side framework.

With great power…

React changes this equation because it can be rendered on the server. Similarly to AngularJS, React root component can be mounted to any node inside your page, but unlike Angular, this page can also be rendered on the server by React.

This opens the door for a whole new class of isomorphic or universal apps, and I have written about it already. What you need to decide is whether you want to render the entire page, or a subset of it. If you choose the latter, then the subsequent question becomes – how do you start the rendering process until React takes over?

My first inclination was to go full React. Using the awesome react-engine module, it is easy to configure React as the view engine in the Express framework, and render the entire page. However, we soon hit some snags:

  1. As we render our UIs using micro services that use UI composition to glue the pages together, we hit a problem of React being grumpy about having to render HTML snippet arriving from outside of its control – something much easier with a templating library such as Dust.js.
  2. JSX turned out to be fairly quirky and finicky when rendering HTML HEAD element, as well as trying to inline JavaScript in tags. In fact, the latter became so error prone that we completely gave up on it, electing to put all our script in files. I didn’t like this particular restriction, and this remains an area where I am sour on JSX and the fact it most decidedly isn’t HTML.

Of course the problems I listed above did not show up in the small example I published in the initial article. They reared their ugly head once we started getting serious. In my original example, the header was a React component. This works great if you control the entire app, but the whole deal of UI composition is to integrate with apps not necessarily written using React, and you can only do that using the least common denominator (HTML, CSS and vanilla JS).

Remind me again about UI composition

In a nutshell, UI composition is the approach where common areas on the page are served as HTML snippets from a REST API. The API service can also serve CSS and JavaScript files that accompany the snippet (if you don’t serve them from a CDN). The idea is that a dedicated microservice can be providing these common areas this way, allowing other microservices to pull the content and inline it in their pages regardless of their stack.

UI composition inverts the flow you would normally use with iframes. Instead of rendering the common areas, then placing an iframe for the content and loading the content from an external URL, we load the common area as HTML and inline it into our page. In the olden days this approach was often accomplished using ‘edge side includes’ or ESIs. This approach has many benefits, including no need for the dreaded iframes, full control over the entire page, and the ability to integrate microservices implemented using different stacks. For example, the teams in my current project use:

  1. Node.js microservices using React for isomorphic rendering
  2. Node.js microservices using Dust.js and jQuery
  3. Java microservices using AngularJS

All of these microservices render the exact same header even though they use different stacks and libraries. Powerful stuff.

OK, so React?

The problem here with React is that when we use it to render the entire page server-side, it starts to squirm in discomfort. Inlining HTML is a problem for React because, while it can be used on the server, it was designed to shine on the client. Inlining raw HTML presumably obtained as a user input into DOM is a major security exposure without sanitization, and React will tell you so in no uncertain terms. Here is the line that inlines the shared header taken straight out of our production code:

<div dangerouslySetInnerHTML={{__html: decodeURIComponent(this.props.header)}} />

This is React telling us very clearly: “I really, really, really don’t like what you are asking me to do”. And this is even before we bring in react-engine. React engine is a PayPal module that enables isomorphism when combined with Node.js/express and react-router. We can render on the server, then pack the properties as part of the HTML response, hydrate the React components on the client and continue where we left off.

Only we have a little problem: notice that in the snippet above we have inlined the header by passing it down to the React component as a prop. What this means is that this prop (‘header’) will be sent to the client alongside other properties. The only problem is that this property contains HTML snippet for the entire header, and because it can really mess up react-engine, it is also URLencoded, making it even bulkier.

This is an unhappy situation: first we inline the header HTML (which is fine), then we send that same inlined HTML, this time encoded, as a React prop to the client. This unnecessarily bloats the generated HTML.


This is what we are going to do to solve this problem: we are going to call back our trusty Dust.js sitting sad on the sidelines ever since we got smitten with React. We can press it into service to do what it does best – outline the page, prep it up to the point where React can take over.

It’s a good thing that Express framework will happily handle more than one view engine. Of course, only one of them can be registered as default, but this just means that we will need to spell out the extension of dust files (because React is the default). Big deal.

var path = require('path')
, express = require('express')
, renderer = require('react-engine')
, dust = require('dustjs-linkedin')
, helpers = require('dustjs-helpers')
, cons = require('consolidate');


// create the view engine with `react-engine`
var engine = renderer.server.create({
  routes: require(path.normalize(__dirname + '/public/routes.jsx')), 
  docType: ""

// set the engines
app.engine('.jsx', engine);
app.engine('.dust', cons.dust);

// set the view directory
app.set('views', __dirname + '/public/views');

// set jsx as the view engine
app.set('view engine', 'jsx');

// finally, set the custom view
app.set('view', renderer.expressView);

Once we have both engines set up, we can arrange our delivery vehicle like this. We will first set up a reusable layout template using Dust.js that will deliver the outline of each page:

<!DOCTYPE html>
   <meta charset='utf-8'>
   <meta http-equiv="X-UA-Compatible" content="IE=edge">
   <meta name="viewport" content="width=device-width, initial-scale=1" >
   <link rel="stylesheet" href="/css/styles.css">
   <div class="main-content">

Notice how inlining of the header now happens in Dust.js, relieving React from doing it. We can now use this template to render our page like this:

<div id="react-mount-node">{spa|s}</div>
<script src="/bundle.js"></script>

We have created a DIV in the template above where we are mounting React, and we will inline the React server-side content using the ‘spa’ variable.

Our Express controller that will handle both Dust.js and React can look something like this:

var request = require("request");

module.exports.get = function(req, res) {
  var settings = {
    title: 'SPA - Demo',
    name: 'React SPA',
    selection: 'header-spa'

  var headerUrl = "http://"+req.headers.host+"/header?selection=header-spa";

  request.get(headerUrl, function (err, response, body) {
    if (err)
      settings.header = body;
    res.render(req.url, { name: settings.name }, function(err, html) {
      if (err) {
        settings.spa = err.message;
        settings.spa = html;
      res.render("spa.dust", settings); 

The code above is what I call ‘React Delivery Vehicle’. It has three steps:

  1. First we fetch the header from the URL that is providing us with the header HTML snippet. We capture it into a variable ‘header’. In production, we will heavily cache this step.
  2. Then we render the React root component as usual. This will employ react-engine and react-router to render all the views necessary for the provided request URL. However, we don’t send the rendering to the response. Instead, we capture it in the variable ‘spa’.
  3. Finally, we invoke Dust.js view engine to render the full page, passing in the ‘settings’ object. This object will contain both the header and the content rendered by React. Dust will simply inline both while rendering the page outline. The result will be sent directly to the Express response.


The solution described above plays to the strengths of both Dust.js as a server side template engine and React as a component library. Dust.js is great at rendering HTML outline the way you would expect, with no need to worry about JSX quirks around HEAD meta tags, or JavaScript inlining. React takes over to render isomorphic components into the mount node. This means we don’t need to send any data that is not needed on the client. This fixes the HTML bloat problem I mentioned before.

As for the negatives, setting up two rendering engines on the server has a slight overhead, and switching mentally from Dust.js to JSX adds context switching tax. Luckily, you can set up reusable Dust.js templates and not really worry about them too much – most of the action will be in JSX anyway.

We like this approach and are currently switching to it across the board. If you have alternative ideas or comments, drop me a line. Meanwhile, the source code for the entire example is available on GitHub as usual, and the sample app employing this mechanism runs on Bluemix.

© Dejan Glozic, 2015


Pessimism as a Service

As far as I can remember, I was forgetful (ironic, I know). I could be driving for ten minutes, wandering why I don’t see the phone Bluetooth symbol on my car’s dash, and realizing I forgot my cellphone at home. Lately, when I reach the door, I ask myself: “OK, what have you forgotten”? Not “have you forgotten anything” but “what”, assuming that an affirmative answer is a forgone conclusion. Such a negative, “guilty until proven innocent” approach saved me many times, but taxed my soul. Am I really that predictable? Is cynicism the only way?

As our super cool, micro-service packed, React supercharged project is picking up steam, I am looking at everything we have done and counting the ways we have deployed ‘Pessimism as a Service’ to production. These examples may seem disconnected to you, but I assure you, there is a cold, calculated thread binding them. Hey, it’s a totally accepted artistic form – my own omnibus, as it were.

Micro services and human nature

I said it before, and I will say it again – micro services are more about people and process than about technology. In his strained attempt to disguise his distaste for micro services, Martin Fowler has still mustered a fainted praise in the way micro services tend to enforce code modularity.

The trouble is that, with a monolithic system, it’s usually pretty easy to sneak around the barrier. Doing this can be a useful tactical shortcut to getting features built quickly, but done widely they undermine the modular structure and trash the team’s productivity. Putting the modules into separate services makes the boundaries firmer, making it much harder to find these cancerous workarounds.

Martin Fowler on Strong Module Boundaries

It this will not inject you with a healthy dose of Weltschmerz, nothing will. What he is saying is that reaching directly into modules instead of using proper interfaces is a tech version of a cookie jar, and instead of counting on your maturity and discipline, micro services simply hide the cookie jar or put it on a top shelf, were you can’t reach it because you skipped the gym too many times.

Large systems are built by real-world organizations, and people are messy, petty, complicated, full of hidden agendas and desires. Engineers who try to look at micro services as a rational system fail to grasp the potent property that requires high emotional intelligence to understand. And it is nothing new – in fact I posit that the first micro service architecture has been practiced by the Nipmuk Indians, living near the lake in today’s Massachusets of the impossible name Chargoggagoggmanchauggagoggchaubunagungamaugg. Translated, it is really a module boundary protocol:

You fish on your side [of the lake], I fish on mine, nobody fishes in the middle.

– Full Indian name for the lake Manchaug, shortened by locals not familiar with micro-service architecture

So, yeah. Ideally, a monolithic system could be highly modular and clean if implemented by highly disciplined, rational people impervious to human foibles. When you manage to hire a teamful of such people, do let me know. In the mean time, the jaded micro service system we are using is humming in production.

AKKA is not a true micro service system

True story – I went to present in the first Toronto Reactive meetup because: (a) I mixed Reactive with React and (b) I wanted to learn what the whole Reactive Manifesto was by presenting on it. Hey, learning by doing!

As such, I was exposed to the AKKA framework. You can read all about Reactive in one of my previous blogs, but suffice to say that AKKA is a framework based on the ‘actor’ pattern and designed specifically to foster an asynchronous, dynamic and flexible architecture that can be deployed to a single server, and then spread out across any number of clusters as the needs grow.

There is a lot to like in AKKA, but I must sadly posit here that it is not a true representative of a micro service system. It is a system inspired by micro services, implementing many of their tenets and with some really nice properties. And yet it betrays one of the key aspects of micro services in that it is not pessimistic. In order to get the benefits of it, you need to lock yourself into a Scala/AKKA stack, paraphrasing the famous Ford Model T joke (you could order it in any color as long as it was black). You lose the ability to choose your stack per micro service.

This property is often misunderstood as a licence for anarchy – a recipe for disaster, cobbling together a concoction of languages, platforms, stacks and runtimes that nobody will be able to keep running and maintain. Of course that unchecked freedom has its price: a real world microservice system will most likely be using only 2-3 stacks (in our case, they ended up being Node.js and Java) and a small number of client side frameworks (for our extended team, React and AngularJS). But there is an ocean of separation between one and two platforms – the former representing lock-in, the latter being freedom.

As I always assume I forgot something, we should always assume that something better is just around the corner, and we don’t want to be hopelessly locked in when it arrives. But we also don’t want to bet our farm on it just yet. This is where the ability to start small is vital: we can try out new approaches in a single micro service without the obligation for a wholesale switch. AKKA requires that we profess our undying love to it and its Scala/JVM stack. Your milage may vary, but I cannot put all my money in that or any other single basket.

React is smart so you can be dumb

On to the client side of the the full stack. My readers know I have expressed my reservation about AngularJS before. I always found its syntax weird, its barrier of entry too high for a practical working system, and that’s before we even mention the version 2.0 schism. However, I always feared I will be viewed as ‘old man that yells at cloud‘ for not recognizing Angular’s genius, until React arrived.

You see, I got React instantly. I didn’t have to scratch my head and re-read its examples. When you read React code, you know exactly what is happening. Of course, that’s because it does less – just the View part. You need to implement Flux for coordinating actions, data stores and views, but Flux is even simpler, and consists of a single dispatcher module you fetch from NPM. You also need something like react-router in order to handle client side page switching. Then you need something like react-engine if you want isomorphic apps (I was told the new term is ‘universal’; I will use both for fun).

You may not fathom the difference in approaches between AngularJS and React until you watch the video explaining React’s design philosophy. You can tell that Facebook deploys React to production. In my opinion, Angular suffers from being designed by rock stars for other rock stars. Once you start getting real and deploying non-trivial apps to production, you need to scale, and that means increasing the number of people that can be productive with your framework of choice. React was designed with the assumption that if the framework is predictable and relatively simple, the velocity can be increased without the proportional increase in the bug rate. Otherwise, what’s the point?

React designers took human nature into account, assumed that we are all dumb at various times of day or week, and ensured that even in those unhappy moments, we can still read our React code and understand what it is doing with relative ease. It feels like a rotten compromise, but it is pure genius.

Web Components just around the corner

Ah, Web Components. The ultimate native component model that will solve Everything. Three years ago there was a lot of excitement, and people jumping on the polyfills to ‘temporarily’ shim the browsers until everybody implements them natively. Fast-forward to November 2015, and today you still cannot bet your project on them in production. Yes, they are natively implemented in Chrome, but if you didn’t want to use IE-only browser extensions 15 years ago, why would you do it when Google, and not Microsoft, is the vendor trying to sell its agenda as a standard.

Yes, there has been some movement on cross-browser support for Web Components, at least when Shadow DOM is concerned. Nevertheless, nothing stands still, and now some aspects of the ES6 module loading are at odds with HTML Imports (an important part of Web Components spec).

And of course, what has also happened in the last three years is that we got React. It has a very strong component model (albeit one that you can only peruse if you lock yourself into React), and more importantly, it extends to the server and even native rendering. This makes React attractive in ways that Web Components will never be able to match.

A year ago, we seriously toyed with the idea of just using shims until Web Components, clearly the future of the component models, arrive. I am glad I allowed my jaded self to prevail and instead used React – it helped us ship to production, with no performance compromises coming from shims, and looking back, we would be nowhere close to the promised glorious future if we allowed exuberance to sway our better judgement.

I am not saying ‘No’ to Web Components forever – they are actually not incompatible with React, and in fact a low-level Web Component can be used just like a native component in a React application, reaping the benefits of the DOM diffing. However, we don’t intend to write Web Components ourselves – we are fully isomorphic and server-side rendering gives us benefits that a comparable Web Component would not.

I predict that Web Components will be the way for incompatible frameworks to co-exist, the way to ‘fish in the middle’ of the Nipmuk lake mentioned above.

Optimism dreams, pessimism ships

These four examples show why enthusiasm and optimism rule the prototypes, meetups and articles, but pessimism takes over in production. Taking human nature into account, rolling with the imperfections of reality, expecting and preparing for the worst pays off tenfold once the projects get serious.

Now, if I can only remember if I turned the stove off before leaving home.

© Dejan Glozic, 2015

With React, I Don’t Need to Be a Ninja Rock Star Unicorn

San Diego Comic-Con 2011 - Lego Ninja, The Conmunity - Pop Culture Geek from Los Angeles, CA, USA

Followers of my blog may remember my microservice period. There was a time I could not shut up about them. Now, several blogs and not a peep. Am I over microservices? Not by a long stretch.

For us, microservices are gravity now. I remember an interview with Billy Corgan of The Smashing Pumpkins where, when pressed about his choice of guitar strings, he answered: “I use them”. That’s how I feel about microservices – now that we live and breathe them every day, they are not exciting, they are air. The only people who get exited about air are SCUBA divers, I suppose, particularly if they are running low.

ReactJS, on the other hand, is interesting to us because we are still figuring it out. For years we were trying to have our cake and eat it too – merge the benefits of server and client side rendering. I guess my answer to ‘vanilla or chocolate ice cream’ is ‘yes please’, and with React, I can have my chocolate sundae for breakfast, lunch and dinner.

The problem with ninja rock star unicorns

The magical creature from the title is of course the sought after 10x developer. He/she knows all the modern frameworks, sometimes reads about the not so modern ones just for laughs, and thrives where others are banging their heads against their desks repeatedly.

Rock star developers not only do not shy away from frameworks with high barrier of entry such as Angular, they often write there own, even more sophisticated and intricate. Nothing wrong with that, except that you cannot hire a full team of them, and even if you could, I doubt team dynamics would be particularly great. The reality of today’s developer job market is that you will likely staff a team with great, competent and potentially passionate developers. I say potentially because in many cases their passion will depend on you as a leader and your ability to instill it.

The React connection

This is where React comes into play. Careful readers of this blog may remember my aversion to JavaScript frameworks in general. For modestly interactive sites, you can go a long way with just Node.js, Express, a templating library such as Dust.js and a sprinkle of jQuery for a good measure. However, a highly dynamic app driven by REST APIs is too much of a challenge for jQuery or vanilla JS alone. I am not saying it cannot be done, but by the same token, while you can cut your grass with box cutters, it is massively less efficient than a lawn mower. At the end of the day, you need the right tools for the right job, and that means some kind of a JavaScript library or a framework.

What kept me away from Angular for the longest time was the opinionated nature of it, and the extent to which it seeks to define your entire world. Angular is a cult – you cannot be in it part time.

“Angular is a cult – you cannot be only a part time member.”

Not an Angular cult member

I have already written about why I got attracted to React from a technical point of view. There are great things you can do with isomorphic apps when you combine great React libraries. But these are all technical reasons. The main reason I am attracted to React is its philosophy.

We are all idiots at times

Angular used to pride itself as a ‘super-heroic JavaScript framework’. Last time I checked, they removed it from the home page (although it still appears in Google searches – ironic, I know). I presume they meant that the framework itself gives you super-hero powers, not that you need to be a super-hero developer in order to use it, but sometimes I felt that way.

I am singling out Angular somewhat unfairly – most MVC JavaScript framework approach the problem by giving you tools to carefully wire up elements on the page with events, react to watched variables, surgically change styles, properties, collections and so on. Sounds great in the beginning, until you scale to a real-world application, and things become really complex.

This complexity may not be a big deal while you are in the thick of it, coding like a beast. You may be a great developer. The problem is that the moment you turn your head away from that code, you start the ‘idiot’ clock – until that time when you no longer remember how everything fits together.

Now, if you are looking at your own code and cannot figure out how it works, what are the chances another team member will? I long ago proclaimed that dumb code is good and smart code is bad. Not bad code, just straightforward, easy to understand, ‘no software patent here’ code. Your future self will be grateful, future maintainers doubly so.

React allows us to write boring code

Let me summarize the key React philosophy in one sentence:

“Something changed in my application’s state. Better re-render it.”

React in a nutshell

I cannot emphasize enough the importance of this approach. It does not say “watch 50 variables and do surgically change DOM elements and properties when something happens in one component, then cascade those surgical changes to other components also watching those components”. Behind this, of course, is React’s ingenious approach of using a virtual DOM and only updating the real DOM with the actual changes between the two. You can read about it on React’s web page.

After many years of ‘surgical’ JavaScript DOM manipulations, there is something completely counter-intuitive about ‘just re-render’ approach. It feels like it should not work. It feels wasteful to keep creating all those JavaScript objects, until you realize that they are really cheap, and that the true cost are actual DOM manipulations.

In fact, you can use this approach with any JavaScript rendering engine – Mustache, Handlebars, Dust. The only problem is – if you try the ‘something changed, re-render the component’ approach there, templates will re-render into inner HTML, and that is wasteful. It is also potentially disruptive if users are interacting with form elements you just recycled under their feet. React, on the other hand, will not do it – it will carefully update the DOM elements and properties around the form controls.

Increase velocity without increasing bug rate

The key design goal of React was to help real world projects running code in production. Developers of modern cloud applications are under constant pressure from product management to increase velocity. The same product management of course expects you to maintain quality of your apps, which is very hard. It is not hard to imagine that shortening the cycles will increase the bug rate, unless the code we write is simplified. Writing ‘surgical’, intricate code in less time is asking for trouble, but React is easy to understand. There is uniformity in its approach, a repeatability that is reassuring and easy for people who didn’t write the code originally to understand when they pick it up.

Developers take great pride in their work, and sometimes they get carried away by thinking that code is their deliverable. They are wrong. What you are delivering are user experiences, and code is just means to an end. In the future, we will just explain what we want to some more powerful Siri or Cortana and our app will come to existence. Until then, we should use whatever allows us to deliver it with high velocity but without bugs that would normally come with it.

For my team, React is just the ticket. As is often in life, YMMV.

© Dejan Glozic, 2015

ReactJS: The Day After

A man with an excruciating headache, Wikimedia Commons
A man with an excruciating headache, Wikimedia Commons

The other day I stumbled upon a funny Onion fake news report of the local man whose one-beer plan went terribly awry. Knowing how I professed undying love to ReactJS in the previous article, and extrapolating from life that after every night on the town comes the morning of reckoning, it is time to revisit my latest infatuation.

Alas, those expecting me to declare my foolishness and heartbreak with ReactJS are hoping in vain. Instead, what you will get here is a sober (ha) account of the problems, gotchas and head scratchers we encountered running ReactJS in production. We continue to use it and plan to build our next set of micro services using it, but we have a more realistic view of it now. So let’s dive in.

  1. Code Splitting – First off, my example didn’t just use ReactJS, but also react-router and react-engine. This amazing trio together allowed us to realize the dream of isomorphic apps, where you start rendering on the server, let the browser quickly render the initial content, load JavaScript, mount React components and continue with the same code on the client.
    Nevertheless, when we got past the small example, we realized that we need to split the code we initially bundled together using browserify. At the time of this writing, code splitting is not entirely painless. React-router in its version 0.13 has examples that all presume the use of Webpack to build your JavaScript. We are using browserify and must suffer until React-router 1.0 arrives. In the mean time, we can use react-router-proxy-loader, which allows us to asynchronously load code from a bundle that does not expect Webpack.

  2. React-engine growing pain – As any new library, react-engine has some rough edges. We are happy to report that one of the issues we had with it (the inability to control how react-router is being instantiated) has already been resolved. We are hoping to be able to make react-engine omit some of the data it sends to the client because it is only ever used for server-side rendering.
  3. ReactJS id properties – React attaches ‘reactid’ data property to almost all DOM elements, using ids that are sometimes very long, resulting in situations like:
    <span data-reactid=".ejv9lnvzeo.$7c87c148-e1a4-4cb8-81f8-c5e74be7684b.">Hello</span>

    If you are using gzip for the markup (as you should), these strings compress very well, but you still end up with a very messy and hard to read HTML when you view source. React team is debating back and forth on the need of these properties and they may disappear at some point in the future. I for one will not miss them.

  4. Fussy with the whitespace – While you may think when working with JSX that you are coding in HTML, you are not, and nowhere is it more apparent than when you try to add some free text in the body of HTML elements, or to mix free text and elements. JSX converts snippets of text into spans at will, resulting in HTML that bears little resemblance to the initial JSX.
    I wish there was a better way to do this. I know all the virtues of React and how JSX is most decidedly not HTML, but some things like free-form text with some embedded tags should not result in a flurry of spans (and the hated data-reactid properties).
  5. Fussy with JavaScript tags – Inserting JavaScript tags in JSX is easy if you are referencing external JS files, but if you try to inline some JavaScript right there, JSX can through you curveball after curveball until you give up and extract that code into a file. This is not a show stopper but it is annoying when you want to inline couple of lines. From the maintainability point of view, it is probably better to keep JavaScript in its own file, so I am not going to protest too loudly.

ReactJS and Web Components

As with any JS framework, making a choice is normally followed by a little nagging voice in your head concerned that you chose wrong. When it comes to religious choices (AngularJS vs ReactJS vs EmberJS etc.), there is little you can do – you just need to make a leap of faith, make sure the framework works for your particular use case and jump.

However, Web Components are something else – they promise to be ‘the native Web’ at some point, so choosing between Web Components and ReactJS is not a religious debate. Even today, with the shims it is possible to run Web Components in browsers not supporting them natively, and natively in Chrome. A growing body of reusable Web components is something you don’t want to be left out of if you are Reactified to the max.

Luckily, Andrew Rota helped out with his presentation on complementarity of ReactJS and Web Components at the recent ReactJS Conf 2015. It is worth the watch, and the skinny is that since about October 2014, custom components are a fair game in JSX. This means that you can place HTML imports in the head element, and then freely use custom components in JSX the same way you would native HTML elements.

In fact, you are not loosing out on the promise of ReactJS virtual DOM. React treats custom components the same way as native HTML components – it will compare your new render to the current DOM state and only change what needs changing (adding, removing, or changing elements and properties that are not the same). This means that you can extend the power of ReactJS to Web Components.

Of course, there are some caveats, but it turns out that things you need to care about when writing Web Components for ReactJS consumption are generally applicable. Writing small components, extremely well encapsulated, that do not leak or make assumptions about the page they are running in, or try to insert stuff outside their own boundary.

No turning back

So this turned to be a click bait of sorts, for we are not turning back from ReactJS, just learning how to use it efficiently and how to be better at it. Stay tuned for the new cool stuff we were able to do with it.

© Dejan Glozic, 2015

PayPal, You Got Me At ‘Isomorphic ReactJS’


I love PayPal’s engineering department. There, I’ve said it. I have followed what Jeff Harrell and the team have been doing ever since I started reading about their wholesale jump into Node.js/Dust.js waters. In fact, their blogs and presentations finally convinced me to push for Node.js in my IBM team as well. I had a pleasure of talking to them at conferences multiple times and I continue to like their overall approach.

PayPal is at its core a no-nonsense enterprise that moved from Java to Node.js. Everything I have seen coming from them had the same pragmatic approach, with concerns you can expect from running Node.js in production – security, i18n, converting a large contingent of Java engineers to Node.js.

More recently, I kept tab on PayPal’s apparent move to from Dust.js to ReactJS. Of course, this time around we learned faster and were already playing with React ourselves (using Dust.js for simpler, content-heavy pages and reserving ReactJS for more dynamic use cases). However, we haven’t really started pushing on ReactJS because I was still looking at how to take advantage of React’s ability to render on the server.

Well, the wait is over. PayPal has won my heart again by releasing a React engine that connects the dots in a way so compatible with what we needed that made me jump with joy. Unlike the version I used for my previous blog post, this one allows server side components to be client-mountable, offering true isomorphic goodness. Finally, a fat-free yogurt that does not taste like paper glue.

Curate and connect

The key importance of PayPal’s engine is in what it brings together. One of the reasons React has attracted so much attention lately is its ability to render into a string on the server, then render to the real DOM on the client using the same code. This is made possible by using NodeJS, which is by now our standard stack (I haven’t written a line of Java code for more than a year, on my honour).

But that is not enough – in order to carry over into the client with the same code, you need ‘soft’ page switching – showing boxes inside other boxes and updating the browser history as these boxes are swapped. This has been brought to us now by another great library – react-router. This module inspired by Ember’s amazing router is quickly becoming ‘the’ router for React applications.

What PayPal did in their engine was connect all these great libraries, then write important glue code to put it all together. It is now possible to mix normal server side templates with pages that start their life on the server, then continue on the client with the state preserved and ready to go as soon as JavaScript is loaded.

Needless to say, this was the solution we were looking for. As far as we are concerned, this will put an end to needless ‘server vs client’ wars, and allow us to have our cake and eat it too. Mmm, cake.

Show us some sample code

OK, let’s get our hands dirty. What many people need when writing applications is a hybrid between a site and an app – the ability to put together a web site that has one or more single-page apps embedded in it. We will build an example site that has two plain ReactJS pages rendered on the server, while the third page is really an SPA taking advantage of react-engine and the ability to go full isomorphic.

We will start by creating a shared layout JSX component to be consumed by all other pages:

var React = require('react');
var Header = require('./header.jsx');

module.exports = React.createClass({

  render: function render() {
    var bundle;

    if (this.props.addBundle)
      bundle = <script src='/bundle.js'/>;

    return (
          <meta charSet='utf-8' />
          <link rel="stylesheet" href="/css/styles.css"/>
          <Header {...this.props}></Header>
          <div className="main-content">

We extracted common header as a separate component that we required and inlined:

var React = require('react');

module.exports = React.createClass({

  displayName: 'header',

  render: function render() {
    var linkClass = 'header-link';
    var linkClassSelected = 'header-link header-selected';

    return (
      <section className='header' id='header'>
        <div className='header-title'>{this.props.title}</div>
        <nav className='header-links'>
            <li className={this.props.selection=='header-home'?linkClassSelected:linkClass} id='header-home'>
              <a href='/'>Home</a>
            <li className={this.props.selection=='header-page2'?linkClassSelected:linkClass} id='header-page2'>
              <a href='/page2'>Page 2</a>
            <li className={this.props.selection=='header-spa'?linkClassSelected:linkClass} id='header-spa'>
              <a href='/spa/section1'>React SPA</a>

The header shows three main pages – ‘Home’, ‘Page2’ and ‘React SPA’. The first two are plain server side pages that are rendered by express and sent to the client as HTML:

var Layout = require('./layout.jsx');
var React = require('react');

module.exports = React.createClass({

  render: function render() {

    return (
      <Layout {...this.props}>
        <p>An example of a plain server-side ReactJS page.</p>

On to the main course

The third page (‘React SPA’) is where all the fun is. Here, we want to create a single-page app so that when we navigate to it by clicking on its link in the header, all subsequent navigations inside it are client-side. However, true to our isomorphic requirement, we want the initial content of ‘React SPA’ page to be rendered on the server, after which react-router and React component will take over.

To show the potential of this approach, we will build a very useful layout – a page with a left nav containing three links (Section 1, 2 and 3), each showing different content in the content area of the page. If you have seen such a page once, you saw it a million times – this layout is internet’s bread and butter.

We start building our SPA top-down. Our top level ReactJS component will reuse Layout component:

var Layout = require('./layout.jsx');
var React = require('react');
var Nav = require('./nav.jsx');
var Router = require('react-router');

module.exports = React.createClass({

  render: function render() {

    return (
      <Layout {...this.props} addBundle='true'>
        <Nav {...this.props}/>
        <Router.RouteHandler {...this.props}/>

We have loaded left nav as a Nav component:

var React = require('react');
var Link = require('react-router').Link;

module.exports = React.createClass({

  displayName: 'nav',

  render: function render() {
    var activeClass = 'left-nav-selected';

    return (
      <section className='left-nav' id='left-nav'>
        <div className='left-nav-title'>{this.props.name}</div>;
        <nav className='left-nav-links'>
            <li className='left-nav-link' id='nav-section1'>
              <Link to='section1' activeClassName={activeClass}>Section 1</Link>
            <li className='left-nav-link' id='nav-section2'>
              <Link to='section2' activeClassName={activeClass}>Section 2</Link>
            <li className='left-nav-link' id='nav-section3'>
              <Link to='section3' activeClassName={activeClass}>Section 3</Link>

This looks fairly simple, except for one crucial difference: instead of adding plain ‘a’ tags for links, we used Link components coming from react-router module. They are the key for the magic here – on the server, they will render normal links, but with ‘breadcrumbs’ allowing React router to mount click listeners on them, and cancel normal navigation behaviour. Instead, they will cause React components registered as handlers for these links to be shown. In addition, browser history will be maintained so that back button and address bar works as expected for these ‘soft’ navigations.

Component RouteHandler is responsible for executing the information specified in our route definition:

var Router = require('react-router');
var Route = Router.Route;

var SPA = require('./views/spa.jsx');
var Section1 = require('./views/section1.jsx');
var Section2 = require('./views/section2.jsx');
var Section3 = require('./views/section3.jsx');

var routes = module.exports = (
  <Route path='/spa' handler={SPA}>;
    <Route name='section1' handler={Section1} />;
    <Route name='section2' handler={Section2} />;
    <Route name='section3' handler={Section3} />;
	<Router.DefaultRoute handler={Section1} />;

As you can infer, we are not declaring all the routes for our site, just the section for the single-page app (under the ‘/spa’ path). There we have built three subpaths and designated React components as handlers for these routes. When a Link component whose ‘to’ property is equal to the route name is activated, the component designated as handler will be shown.

Server needs to cooperate

In order to get our HTML5 push state enabled router to work, we need server side cooperation. In the olden days when SPAs were using hashes to ensure client side navigation is not causing page reloading, we didn’t need to care about the server because hashes stayed on the client. Those days are over and we want true deep URLs on the client, and we can have them using HTML5 push state support.

However, once we start using true links for everything, we need to tell the server to not try to render pages that belong to the client. We can do this in express like this:

app.get('/', function(req, res) {
  res.render('home', {
    title: 'React Engine Demo',
    name: 'Home',
    selection: 'header-home'

app.get('/page2', function(req, res) {
  res.render('page2', {
    title: 'React Engine Demo',
    name: 'Page 2',
    selection: 'header-page2'

app.get('/spa*', function(req, res) {
  res.render(req.url, {
    title: 'SPA - React Engine Demo',
    name: 'React SPA',
    selection: 'header-spa'

Notice that we have defined controllers for two routes using normal ‘res.render’ approach, but the third one is special. First off, we have instructed express to not try to render any pages under /spa by sending them all to the React router. Notice also that instead of sending normal view names in res.render, we are passing entire URL coming from the request. This particular detail is what makes ‘react-engine’ ingenious – the ability to mix react-router and normal views by looking for the presence of the leading ‘/’ sign.

A bit more boilerplate

Now that we have all these pieces, what else do we need to get this to work? First off, we need the JS file to configure the react router on the client, and start the client side mounting:

var Routes = require('./routes.jsx');
var Client = require('react-engine/lib/client');

// Include all view files. Browserify doesn't do
// this automatically as it can only operate on
// static require statements.
require('./views/**/*.jsx', {glob: true});

// boot options
var options = {
  routes: Routes,

  // supply a function that can be called
  // to resolve the file that was rendered.
  viewResolver: function(viewName) {
    return require('./views/' + viewName);

document.addEventListener('DOMContentLoaded', function onLoad() {

And to round it all, we need to deliver all this JavaScript, and JSX templates, to the client somehow. There are several ways to approach JavaScript modularization on the client, but since we are using Node.js and sing the isomorphic song, what can be more apt than using Browserify to carry over CommonJS into the client? The following command line will gather the entire dependency tree for index.js into one tidy bundle:

browserify -t reactify -t require-globify public/index.js -o public/bundle.js

If you circle back all the way to Layout.jsx, you will notice that we are including a sole script tag for /bundle.js.

The complete source code for this app is available on GitHub. When we run ‘npm install’ to bring all the dependencies, then ‘npm start’ to run browserify and start express, we get the following:


When we click on header links, they cause full page reload, rendered by express server. However, clicks on the left nav links cause the content of the SPA page to change without a page reload. Meanwhile, the address bar and browser history is dutifully updated, and deep links are available for sharing.


You can probably tell that I am very excited about this approach because it finally brings together fast initial rendering and SEO-friendly server-side pages, with full dynamic ability of client side apps. All excitement aside, we need to remember that this is just views – we would need to write more code to add action dispatcher and data stores in order to implement full Flux architecture.

Performance wise, the combined app renders very quickly, but one element sticks out. Bundle.js in its full form is about 800KB of JavaScript, which is a lot. When running the command to minify it, it is trimmed down to 279KB, and when compression is enabled in express, it goes further down to 62.8KB to send down the wire. We should bear in mind that this is ALL JavaScript we need – ReactJS, as well as our own components. It should also be noted that this JavaScript is loaded asynchronously and that we are sending content from the server already – we will not see a white page while script is being downloaded and parsed.

In a more complex application, we would probably want to segregate JavaScript into more than one bundle so that we can load code in chunks as needed. Luckily, react-router already addressed this.

The app is deployed on Bluemix – you can access it at http://react-engine-demo.mybluemix.net. Try it out, play with the source code and let me know what you think.

Great job, PayPal! As for me, I am completely sold on ReactJS for most real world applications. We will be using this approach in our current project from now on.

© Dejan Glozic, 2015

The Art of Who Does What

Jacob Duck, Dividing the Spoils, 1635, Wikimedia Commons
Jacob Duck, Dividing the Spoils, 1635, Wikimedia Commons

Job posting: If you like my blog and would like to work on the stuff I write about, come and join my Toronto team.

Novelist Erich Maria Remarque claimed in one of his novels that civilization is a thin veneer, covering the primal urges of savages ready to grab each others’ throats at a moment’s notice. You can attest to that at times of temporary breakdowns such as power outages, elevator malfunctions, or heated sports events. In the relatively rational and orderly corridors of corporate life, nothing brings the primitive reptilian brain to the forefront like the activity of divvying up the work.

There are perfectly rational explanations for why this happens. Work is a big part of our identity. It is now spilling out into our personal brand as well – your LinkedIn and Twitter profiles say what you do for living. You will go great lengths and exert a lot of effort in order to move that needle from ‘Something’ to ‘Architect Something’ to ‘Senior Architect Something’. You want these changes to reflect on your LinkedIn profile as an upward progression, a well managed and deliberate career narrative.

Titles aside, most people want to do meaningful work, and want to grow their career by kicking ass, not by marking the time. A precondition for this is to be assigned a great and meaningful task that you can crush, being amazing as you are.

Divvy up

In corporations large and small, there comes a time where in one part of the room, you have a few nervous people, and in another, a pile of stuff to be done. Call it a work pie – it has to be cut and divided among them. Now remember the ‘civilization as a thin veneer’ and you can imagine the emotional undercurrents of such a situation.

Divvying up the work is tightly connected to hiring, and those two activities may act like the chicken and the egg in many situations. The amount of work is also very important. If this is the only pie to divide, tensions will be much higher than if the pies keep coming – people who didn’t get their piece will be much more relaxed if a new one will arrive in 5 minutes.

In my professional life, I have observed several situations I will try to enumerate here.

Grow with work

What is more fitting to start with than, well, a startup. When you have two starry-eyed founders and a lofty vision (according to HBO’s Silicon Valley, which must include a desire to ‘make the world a better place’), there is this infinite pie that never gets smaller no matter how much you cut it. Founders work day and night and ‘who does what’ discussion is very short and efficient. Nothing will matter if work is not done before the VC money runs out, so getting it done is primary consideration.

According to the guys of 37signals, most startups are careful with hiring and really only hire when they reach practical limits.

The right time to hire is when there’s more work than you can handle for a sustained period of time.

Jason Fried & David Heinemeier Hansson, ‘Rework’

In this mode, dividing the work is a low ceremony affair – everybody wears many hats, and there is a sense of ‘we are all in this together’. This is a good phase.

Lions eat first

When companies are growing quickly and they are having a lot of impact, careers take care of themselves. And when companies aren’t growing quickly or their missions don’t matter as much, that’s when stagnation and politics come in.

Google’s Erich Schmidt to Sheryl Sandberg

When Facebook’s Sheryl Sandberg got this advice from Google CEO Erich Schmidt, it highlighted the moment when the pendulum swings and there is more people than work. In most real world organizations, the amount of things to do grows and shrinks faster than the teams do. After all, you cannot be hiring and firing people all the time – it is expensive and bad for morale.

In those situations, politics goes into full swing, and managers closer to the executives in control of the pie get the choicest pieces, leaving the scraps for the less connected and less savvy. This was and still is a reality in many big corporations to one degree or another, but things are changing there as well. New organizational trends already brought us flatter structures. Matrixed organizations with feature teams are more often the norm, with models like the one used by Spotify being all the rage recently.

There are varying reasons why certain teams tend to run away with key pieces of the mission. They can have a track record of delivery, which is fair. They can also have a critical mass required to take on an important mission. They can also be tapped to own the technical area (say, compilers) and have the expertise. But sometimes there is the inertia that crosses over into politics. A team that traditionally owned an area may be a bad choice to take that technology to the cloud because of the skills mismatch. In many of these discussions, the results will not seem fair to the outside observer not in on the subtle political undercurrents of the situation.

Second wind

A comical side-effect of the ‘lions eat first’ model is that eventually lions get stuffed silly and cannot take another bite. In my time, I was often far from the main power centres, so I developed the art of the second wind to perfection. Here how it is plaid:

  1. The first pie arrives to the table
  2. Lions eat first, stuff themselves until they cannot breathe
  3. After a while, an unexpected pie arrives. Lions watch it with sad eyes, unable to do anything.
  4. You jump in and run away with the whole new pie.

As I said before, this all depends on the availability of the new pie. But even in the olden days it was possible. The first division of ‘who does what’ is normally based on the very imprecise ideas of what the new project is all about. After a while, reality sets in, holes are identified, new requirements emerge, and this is where you can jump in and get that work.

Or you can invent a whole new pie. You can actively look for gaps in the vision, notice the opportunity, prototype something and demo it to the executives. When there is not enough pie on the table, create more by innovating.

Note that this model is becoming more of a norm lately. Everything is speeding up, cycles are getting shorter, feature teams (or should I say ‘squads’) are formed and dissolved at a faster rate. This is good news, because there is nothing like office politics to sap enthusiasm and energy from bright and starry-eyed new hires. I am happy we are slowly moving away from politics-ledden job partition, if only out of necessity brought on by the tectonic shifts in the industry.

Getting ahead of the HR curve

Alas, where there are people, there will always be some amount of politics. The corporation does not even have to be that big to get into the bizarre game of req tickets:

Reqs vanish randomly, often without notice, without reason, and at the least convenient time.

Rands in Repose

First of all, if you have hiring tickets, congratulations – it means you are on a project that is growing (assuming these are not backfills). You may even be in the coveted ‘startup in a large organization’ situation, where you are trying to grow a 1.0 project and are staffing like crazy.

This is an often comical situation because you are trying to be two things at the same time. You are trying to move fast, build a team and be nimble, while at the same time dealing with a corporate machine that is not designed for that. You are growing against a fluid plans and visions that change daily (or should I say ‘pivot’). And you never know when the executives championing the new startup culture will succumb to bean counters’ nagging and rein in the mad hiring sprout.

You could say that true startups grow with concrete work, and that this is not a very startup-like behaviour, and you would be right. However, there is logic to it:

  1. You are growing a team with a general skill set, kind of like a local competency centre, or to use the Spotify parlour, a ‘chapter’. You can form guilds as needed, but your chapter will be more stable and build an enviable track record that will attract new work in the future.
  2. You are building a centre of gravity that will assist you in the upcoming ‘who does what’ discussions. You want to be the path of least resistance for tasks that look related and up your team’s skill alley.
  3. And of course, a req ticket unused is a req ticket lost.

Be the baker

Based on everything I said so far, it appears that in order to change the conversation, it is better to ensure that pies are coming than to entangle in the ugly politics of wrestling over a scarce resource. Build a team of great skilled developers, preferably able to do full-stack development and do many things with aplomb, and then unleash the innovation that creates new pies out of thin air. It is better to be the one creating the new work than fighting over it.

Now if you excuse me, all this talk about pie made me hungry. Mmmm, pie.

© Dejan Glozic, 2015

Same Company, New Job

Verrazano-Narrows Bridge: The Beginning, Metropolitan Transportation Authority of the State of New York, Wikimedia Commons
Verrazano-Narrows Bridge: The Beginning, Metropolitan Transportation Authority of the State of New York, Wikimedia Commons

If you read my bio, you can find out that I come from Europe. In that part of the world, if you hop in a car and drive in any direction, you will enter another country that same day. In contrast, you can drive thousands of miles, cross three time zones and many different geographic and climate regions and still be in the USA. Many people there had rich lives doing very different things while never really needing their passport.

I feel the same about career change. In Silicon Valley, people normally switch companies when they feel like doing something different, because companies are small, young and focused. But when you work for a company as large and multi-faceted as IBM, you have the other option – to change what you are working on without having to go through the new employee orientation again and learn where coffee is. And that is exactly what I am doing.

I am moving on to a new job, from DevOps to Data Analytics. I don’t need to spend a lot of time making a case why cloud data and analytics is currently exploding as an area. The amount of data we are amassing is unprecedented and relentlessly growing. With the new data that IoT devices will bring to the table in the coming years, we have a dire need to collect, store and most importantly, make some sense of it all, otherwise what’s the point?

Of course, I was not looking for an entirely clean start. I spent more than a year blogging about Node.js, micro-services, message brokers, authentication, UI composition. I simply intend to employ all the great stuff I have carefully curated for presenting and visualizing the data and the results of data analytics in the cloud. All the lessons of clustering, high availability, caching and DevOps automation will also come in handy in the new job. In other words, what is changing is ‘What’ but not the ‘How’ part of the equation.

Come join me

In the book ‘Being Geek’ by Michael Loop (aka Rands in Repose), the following section in the chapter ‘The Deliberate Career’ best describes my next adventure:

A start-up is more likely to be in a state where it’s hiring lots of people, aggressively attacking new problems, and having a sense of urgency. Still, you can find the same attributes in a large company in a specific group that has been tasked with the new and sexy. This hybrid might be the best of both worlds – the urgency of a start-up supported by the stability of an established company.

As far as large companies go, there is rarely something as thrilling and filled with opportunities as being at the beginning of a 1.0 version of a product or service. And to further underline the similarity, we would not be a start-up (even in an established company) if we were not aggressively hiring.

If you live in Toronto, have enjoyed my blog so far (or are intrigued by this post and binge-read it backwards), and like the following areas:

  • Node.js micro-services
  • Dust.js
  • HTML5/CSS3
  • Angular, Backbone, React, Web Components
  • Message brokers
  • Web sockets

come and join the team I am building. Drop me an email, tweet me a message, send me a carrier pigeon – whichever way you choose to reach me, but remember: we have a sense of urgency, so don’t take too long. This stuff will not get built on its own.

© Dejan Glozic, 2015