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ClojureScript Year In Review

23 December 2015

It’s been a very exciting year for ClojureScript. It’s clear that things have been accelerating and here is a personal selection of highlights:


While technically it appeared in late 2014, CLJSJS took off when ClojureScript landed enhanced and standardized support for foreign dependencies in January. Thanks to the tireless work of many contributors, the wider community of ClojureScript users can now leverage the most popular JavaScript libraries with minimal hassle. Many thanks to Martin Klepsch and Juho Teperi for leading the charge.


2015 kicked off with a near complete rewrite of the ClojureScript REPL infrastructure. This was an admittedly painful transition, but now that we are on the other side of the hump the considerable payoff is self-evident.

Case in point, Mike Fikes’s Ambly REPL delivers a seamless live experience when developing iOS applications without requiring tethering or XCode beyond the initial install. Using a slick combination of Bonjour and WebDAV, the Ambly REPL sets a new bar.

Here’s a basic Ambly demo:

Ambly plays well with other cool JavaScriptCore integrations like Ejecta which exposes both JavaScript Canvas 2D and WebGL APIs to native iOS clients.

For example here’s Ambly being used to develop an Ejecta application on tvOS:

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You can find out more here;

React Native

Facebook announced React Native further solidifying the role of React as a critical part of the ClojureScript ecosystem. ClojureScript React bindings abound and now the community can easily reach the iOS and Android platforms using the same React bindings we’ve all come to love over the past two years.

Here is another Mike Fikes video demonstrating React Native with Reagent:

For getting up and running with React Native, look at natal and re-natal as well as the collection of resources at

Suffice to say I see ClojureScript + React Native really taking off in 2016.

Google Summer of Code

The ClojureScript Google Summer of Code 2015 project was a smashing success. Maria Geller dove deep into the problem of integrating CommonJS, AMD, ES2015 modules as well as integrating popular JavaScript compilation technology like Babel.js. There’s more work to do but the future is bright for good integration with the wider JavaScript ecosystem. You can read more about the project here.

Also Maria Geller gave a stunning talk about the ClojureScript compiler internals at the Clojure/conj which is well worth watching.


Reagent has become the tool of choice for many people in the ClojureScript community. My uninformed impression is that this has been further bolstered by the appearance of re-frame, a very well-considered architecture for Reagent applications.

If the other ClojureScript React bindings aren’t your speed, Reagent and re-frame invite close assessment. The community is prolific, active, and helpful.


While Figwheel appeared prior to 2015, it became clear with a slew of strong stable releases that, Bruce Hauman is one of ClojureScript’s finest tooling authors. In a very short window of time Figwheel has taken the ClojureScript world by storm as the REPL of choice. The usefulness of hot-code loading during UI work cannot be overstated.

This video should be watched in its entirety.


Clearly Figwheel wasn’t enough for Bruce. Devcards sets a new bar for UI tooling. Devcards also came together prior to 2015 but the adoption rate has skyrocketed of late and for good reason. Having tried all kinds of UI tooling in my career, Devcards legitimately provides something so obvious and simple it’s incredible it hasn’t been tried before. As Alan Kay sez, a change of perspective is worth a non-trivial amount of IQ points.

Combined with Figwheel, Devcards provides an interactive way to both develop and view component states, radically simplifying the task of testing your UI work:

Again, this video must be watched in its entirety.

Self Compilation

With the appearance of reader conditionals in Clojure 1.7.0 I got the bug over the summer to make ClojureScript self compile. While it may seem like a feat to outsiders, ClojureScript was always ready for self compilation and the work was pretty boring. The repercussions however are only starting to be understood. Some great examples of the power of optional bootstrapping are the winning Clojure Cup entry and a new web based ClojureScript REPL.

Some other neat bootstrapping projects follow after some brief words on ClojureScript 1.7.X.

ClojureScript 1.7.X

Shortly after bootstrapping we released ClojureScript 1.7.28. This was the first release of ClojureScript with a proper version number. It also signified a much slower pace for releases, much needed to avoid tooling churn. Now that the fundamentals are in place expect 2016 releases to be heavily focused on compiler performance and build reliability. Master already includes exciting enhancements like parallel builds (40 lines of code written during a 45 minute train ride - thanks Clojure!). Users have reported 30-300% faster compile times on their multi-core machines.


Mike Fikes is clearly a tireless person, within what seemed like hours of bootstrapping, Mike Fikes had a standalone ClojureScript REPL that you can easily install with brew.

If you want a ClojureScript REPL that starts fast for testing one liners, look no further than Planck.


Thanks to bootstrapping you can also use full blown ClojureScript on your iPhone or iPad:

If you had told me I would be running a robust dialect of Clojure on my iOS device four years ago I would have laughed in disbelief.


This one came out of the blue. Lisp is 58 years old and people are still coming up with things that no one has tried before. With a clever algorithm and some inference driven by indentation, Shaun LeBron of has probably created the most beginner friendly way to write Lisp the world has ever seen. The parinfer blog post is a jaw dropper.

And of course Mike Fikes gets parinfer into Replete in short order:

If anything 2015 has been the year of network effects. It’s thrilling to see all these individual efforts come together as part of a grand shared vision.


Cursive IDE shipped! If you’re looking for a rich development environment for Clojure and ClojureScript, Cursive delivers in spades. I’ve been using it exclusively for Clojure and ClojureScript development since January and I can’t imagine life without it.

Cider 0.10

Cider 0.10 shipped with many, many enhancements for ClojureScript. If Emacs is your tool of choice, the ClojureScript story has improved leaps and bounds over the past year thanks to the tireless work of many contributors.

Om Next

I also did a series of talks on Om Next this year. Whether or not you adopt Om or the technologies that inspired it (Relay, Falcor, Datomic), I am confident that Graph-Query-View based UI architectures will gain steam in 2016. Kovas Boguta and I gave a high level talk at QCon and I delivered the nitty gritty at Clojure/conj.


The amount of innovation and invention in the ClojureScript community is nothing short of stunning. Hopefully this post gives you a sense of what sets ClojureScript apart from pretty much every other compile-to-JavaScript technology. As a group we are now thinking far beyond programming language esoterica and have turned towards the challenge of building the necessary environmental infrastructure required for the construction of simpler and more robust software systems.

Congratulations to all that have given to the evolution of ClojureScript whether through adoption, contribution, or evangelism!

I suspect 2016 will be an even bigger one for ClojureScript.

Have a Happy New Year!