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A truly modular frontend framework


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A truly modular frontend framework

To understand what I mean by truly modular just read the source


Hello world

'use strict';
var document = require('global/document');
var hg = require('mercury');
var h = require('mercury').h;
function App() {
    return hg.state({
        value: hg.value(0),
        channels: {
            clicks: incrementCounter
function incrementCounter(state) {
    state.value.set(state.value() + 1);
App.render = function render(state) {
    return h('div.counter', [
        'The state ', h('code', 'clickCount'),
        ' has value: ' + state.value + '.', h('input.button', {
            type: 'button',
            value: 'Click me!',
            'ev-click': hg.send(state.channels.clicks)
};, App(), App.render);

Basic Examples

Intermediate Examples

Unidirectional examples

The following examples demonstrate how you can mix & match mercury with other frameworks. This is possible because mercury is fundamentally modular.

Disclaimer: The following are neither "good" nor "bad" ideas. Your milage may vary on using these ideas


Mercury vs React

mercury is similar to react, however it's larger in scope, it is better compared against om or quiescent

  • mercury leverages virtual-dom which uses an immutable vdom structure
  • mercury comes with observ-struct which uses immutable data for your state atom
  • mercury is truly modular, you can trivially swap out subsets of it for other modules
  • mercury source code itself is maintainable, the modules it uses are all small, well tested and well documented. you should not be afraid to use mercury in production as it's easy to maintain & fix.
  • mercury encourages zero dom manipulation in your application code. As far as your application is concerned elements do not exist. This means you don't need to reference DOM elements when rendering or when handling events
  • mercury is compact, it's 11kb min.gzip.js, that's smaller than backbone.
  • mercury strongly encourages FRP techniques and discourages local mutable state.
  • mercury is highly performant, it's faster then React / Om / ember+htmlbars in multiple benchmarks TodoMVC benchmark
    animation benchmark TodoMVC benchmark source
  • mercury comes with FP features like time-travel / easy undo out of the box.
  • mercury is lean, it's an weekend's read at 2.5kloc. (virtual-dom is 1.1kloc, an evening's read.) compared to react which is almost 20kloc (a month's read)


mercury is a small glue layer that composes a set of modules that solves a subset of the frontend problem.

If mercury is not ideal for your needs, you should check out the individual modules and see if you can re-use something.

Alternatively if the default set of modules in mercury doesn't work for you, you can just require other modules. It's possible to for example, swap out vtree with react or swap out observ-struct with backbone

See the modules README for more information.


See the documentation folder


See the FAQ document


WIP. In lieu of documentation please see examples :(


npm install mercury


If you want to develop on mercury you can clone the code

git clone
cd mercury
npm install
npm test

npm run tasks

  • npm test runs the tests
  • npm run jshint will run jshint on the code
  • npm run disc will open discify (if globally installed)
  • npm run build will build the html assets for gh-pages
  • npm run examples will start a HTTP server that shows examples
  • npm run dist will create a distributed version of mercury
  • npm run modules-docs will (re)generate docs of mercury modules


A lot of the philosophy and design of mercury is inspired by the following:

  • react for documenting and explaining the concept of a virtual DOM and its diffing algorithm
  • om for explaining the concept and benefits of immutable state and time travel.
  • elm for explaining the concept of FRP and having a reference implementation of FRP in JavaScript. I wrote a pre-cursor to mercury that was literally a re-implementation of elm in javascript (graphics)
  • reflex for demonstrating the techniques used to implement dynamic inputs.


  • Raynos
  • Matt-Esch
  • neonstalwart
  • parshap
  • nrw
  • kumavis

MIT Licenced