Various programming stuff

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Using browserify and watchify to improve your client-side-javascript workflow

The problem

Once upon a time, when people started using client-side code to their projects they (mainly due to the lack of decent client-side libraries but also because of the NIH syndrome) were just adding their own code in script nodes or .js files using document.getElementById to manipulate the DOM (good luck checking for all possible browser-edge cases) and window.XMLHttpRequest to try doing AJAX.

After these dark-times, the age of javascript-framework came: prototype, jquery, dojo. These were (and still are) some great libraries (even NIH-sick people used them to handle browser incompatibilities): You just downloaded the .js file with the framework, put it inside your project static files and added it to your page with a script tag and then filled your client-side code with funny $(‘#id’) symbols!

Coming to the modern age in client-side development, the number of decent libraries has greatly increased and instead of monolithic frameworks there are different libraries for different needs. So instead of just downloading a single file and adding the script node for that file to your HTML, you need to download the required javascript files, put them all in your static files directory and then micro-manage the script nodes for each of your pages depending on which libraries each page needs! So if you want to use (for example) moment.js to your client-side code you need to go to all HTML pages that use that specific client-side code and add a moment.js-script element!

As can be understood this leads to really ugly situations like people avoiding refactoring their code to use external libraries, using a single-global module with all their client side code, using CDN to avoid downloading the javascript libraries and of course never upgrade their javascript libraries!

The solution

browserify and watchify are two sister tools from the server-side-javascript (node.js and friends) world that greatly improve your javascript workflow: Using them, you no longer need to micro-manage your script tags but instead you just declare the libraries each of your client-side modules is using - or you can even create your own reusable modules! Also, installing (or updating) javascript libraries is as easy as running a single command!

How are they working? With browserify you create a single main.js for each of your HTML pages and in it you declare its requirements using require. You’ll then pass your main.js through browserify and it will create a single file (e.g bundle.js) that contains all the requirements (of course each requirement could have other requirements - they’ll be automatically also included in the resulting .js file). That’s the only file you need to put to the script tag of your HTML! Using watchify, you can watch your main.js for changes (the changes may also be in the files included from main.js) and automatically generate the resulting bundle.js so that you’ll just need to hit F5 to refresh and get the new version!

browserify not only concatenates your javascript libraries to a single bundle but can also transform your coffesscript, typescript, jsx etc files to javascrpt and then also add them to the bundle. This is possible through a concept called transforms — there are a lot of transforms that you can use.

Below, I will propose a really simple and generic workflow that should cover most of your javascript needs. I should mention that I mainly develop django apps and my development machine is running windows, however you can easily use exactly the same workflow from any kind of server-side technology (ruby, python, javascript, java, php or even static HTML pages!) or development machine (windows, linux, osx) - it’s exactly the same!

Installing required tools

As already mentioned, you need two node.js tools. Just install them globally using npm (installing node.js and npm is really easy - there’s even a package for windows):

npm install -g browserify watchify

The -g switch installs the packages globally so you can use the browserify and watchify commands from your command prompt - after that entering browserify or watchify from your command prompt should be working.

Starting your (node.js) project

Although you may already have a project structure, in order to use browserify you’ll need to create a node.js project (project from now on) that needs just two things:

  • a package.json that lists various options for your project
  • a node_modules directory that contains the packages that your project uses

To create the package.json you can either copy paste a simple one or run npm init inside a folder of your project. After npm init you’ll need to answer a bunch of questions and then a package.json will be created to the same folder. If you don’t want to answer these questions (most probably you only want to use node.js for browserify - instead you wouldn’t be reading this) then just put an empty json string {} in package.json.

I recommend adding package.json to the top-level folder of your version-controlled souce-code tree - please put this file in your version control - the node_modules directory will be be created to the same directory with package.json and should be ignored by your version control.

Running browserify for the first time

Not the time has come to create a main.js file. This could be put anywhere you like (based on your project structure) - I” suppose that main.js is inside the src/ folder of your project. Just put a console.log("Hello, world") to the main.js for now. To test that everything is working, run:

browserify src/main.js

You should see some minified-js gibberish to your console (something like (function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof ...) ) which means that everything works fine. Now, create a dist directory which would contain your bundle files and run

browserify src/main.js -o dist/bundle.js

the -o switch will put the the same minified-js gibberish output to the dist/bundle.js file instead of stdout. Finally, include a script element with that file to your HTML and you should see “Hello, world” to your javascript console when opening the HTML file!

Using external libraries

To use a library from your main.js you need to install it and get a reference to it through require. Let’s try to use moment.js: To install the library run

npm install moment --save

This will create a moment directory inside node_modules that will contain the moment.js library. It will also add a dependency to your package.json (that’s what the --save switch does), something like this:

"dependencies": {
  "moment": "^2.10.3"

Whenever you install more client-side libraries they’ll be saved there. When you want to re-install everything (for instance when you clone your project) you can just do a

npm install

and all dependencies of package.json will be installed in node_modules (that’s why node_modules should not be tracked).

After you’ve installed moment.js to your project change src/main.js to:

moment = require('moment')
console.log(moment() );

and rerun browserify src/main.js -o dist/bundle.js. When you reload your HTML you’ll see the that you are able to use moment - all this without changing your HTML!!!

As you can understand, in order to use a library with browserify, this library must support it by having an npm package. The nice thing is that most libraries already support it — let’s try for another example to use underscore.js and (for some reason) we need version underscore 1.7 :

npm install underscore@1.7--save

you’ll se that your package.json dependencies will also contain underscore.js 1.7:

  "dependencies": {
    "moment": "^2.10.3",
    "underscore": "^1.7.0"

If you want to upgrade underscore to the latest version run a:

npm install underscore --upgrade --save

and you’ll see that your package.json will contan the latest version of underscore.js.

Finally, let’s change our src/man.js to use underscore:

moment = require('moment')
_ = require('underscore')

_([1,2,3]).map(function(x) {

After you create your bundle you should se 2 3 4 in your console!

Introducing watchify

Running browserify every time you change your js files to create the bundle.js feels like doing repetitive work - this is where wachify comes to the rescue; watchify is a tool that watches your source code and dependencies and when a change is detected it will recreate the bundle automagically!

To run it, you can use:

watchify src/main.js -o dist/bundle.js -v

and you’ll see something like: 155544 bytes written to dist/bundle.js (0.57 seconds) — try changing main.js and you’ll see that bundle.js will also be re-written!

Some things to keep in mind with watchify usage:

  • The -v flag outputs the verbose text (or else you won’t se any postive messages) - I like using it to be sure that everything is ok.
  • You need to use the -o flag with watchify — you can’t output to stdout(we’ll see that this will change our workflow for production a bit later)
  • watchify takes the same parameters with browserify — so if you do any transformations with browserify you can also do them with watchify

In the following, I’ll assume that you are running the watchify src/main.js -o dist/bundle.js -d so your bundles will always be re-created when changes are found.

Creating your own modules

Using browserify we can create our own modules and require them in other modules using the module.exports mechanism!

Creating a module is really simple: In a normal javascript file either assign directly to module.exports or include all local objects you want to be visible as an attribute to module.exports — everything else will be private to the module.

As an example, let’s create an src/modules folder and put a file module1.js inside it, containing the following:

var variable = 'variable'
var variable2 = 'variable2'
var funct = function(x) {
  return x+1;
var funct2 = function(x) {
  return x+1;

module.exports['variable'] = variable
module.exports['funct'] = funct

As you see, although we’ve defined a number of things in that module, only the variable and funct attributes of module.exports will be visible when the module is used. To use the module, change main.js like this:

module1 = require('./modules/module1')

When you refresh your HTML you’ll see 10 in the console. So, require will return the module.exports objects of each module. It will either search in your project’s node_modules (when you use just the modfule name, for example moment, or locally (when you start a path with either ./ or ../ — in our case we required the module module1.js from the folder modules).

As a final example, we’ll create another module that is used by module1: Create a file named module2.js inside the modules folder and the following contents:

var funct = function(x) {
    return x+1;

module.exports = funct

After that, change module1.js to this:

module2 = require('./module2')

var variable = 'variable'
var funct = function(x) {
    return module2(x)+1;

module.exports['variable'] = variable
module.exports['funct'] = funct

So module1 will import the module2 module (from the same directory) and call it (since a function is assignedd to module.exports). When you refresh your HTML you should see 11!

Uglifying your bundle

If had taken a look at the file size of your bundle.js when you’d included moment.js or underscore.js you’d see that the file size has been greatly increased. Take a peek at bundle.js and you’ll see why: The contents of the module files will be concatenated as they are, without any changes! This may be nice for development / debugging, however for production we’d like our bundle.js to be minified — or uglyfied as it’s being said in the javascript world.

To help us with this, uglifying we’ll use uglify-js. First of all, please install it globally

npm install uglify-js -g

and you’ll be able to use the uglifyjs command to uglify your bundles! To use the uglifyjs command for your bundle.js try this

uglifyjs dist\bundle.js  > dist\bundle.min.js

and you’ll see the size of the bundle.min.js greatly reduced! To achieve even better minification (and code mangling as an added bonus) you could pass the -mc options to uglify:

uglifyjs dist\bundle.js -mc > dist\bundle.min.js

and you’ll see an even smaller bundle.min.js!

As a final step, we can combine the output of browserify and uglify to a single command using a pipe:

browserify src/main.js | uglifyjs -mc > dist/bundle.js

this will create the uglified bundle.js! Using the pipe to output to uglifyjs is not possible with watchify since watchify cannot output to stdout — however, as we’ll see in the next section this is not a real problem.

The client-side javascript workflow

The proposed client-side javascript workflow uses two commands, one for the development and one for creating the production bundle.

For the development, we’ll use watchify since we need to immediately re-create the bundle when a javascript source file is changed and we don’t want any uglification:

watchify src/main.js -o dist/bundle.js -v

For creating our production bundle, we’ll use browserify and uglify:

browserify src/main.js  | uglifyjs -mc warnings=false > dist/bundle.js

(i’ve added warnings=false to uglfiyjs to suppress warnings).

The above two commands can either be put to batch files or added to your existing workflow (for example as fabric commands if you use fabric). However, since we already have a javascrpt project (i.e a package.json) we can use that to run these commands. Just add a scripts section to your package.json like this:

  "dependencies": {
    "moment": "^2.10.3",
    "underscore": "^1.8.3"
  "scripts": {
    "watch": "watchify src/main.js -o dist/bundle.js -v",
    "build": "browserify src/main.js  | uglifyjs -mc warnings=false > dist/bundle.js"

and you’ll be able to run npm run watch to start watchifying for changes and npm run build to create your production bundle!


In the above we saw two (three if we include uglifyjs) javascript tools that will greatly improve our javascript workflow. Using these we can easily require (import) external javascript libraries to our project without any micromanagement of script tags in html files. We also can seperate our own client-side code to self-contained modules that will only export interfaces and not pollute the global namespace. The resulting production client-side javascript file will be output minimized and ready to be used by the users’ browsers.

All the above are possible with minimal changes to our code and development workflow:

  • create a package.json and install your dependencies
  • require the external libraries (instead of using them off the global namespace)
  • define your module’s interace through module.exports (instead of polluting the global namespace)
  • change your client javascript files to bundle.js
  • run npm run watch when developing and npm run build before deploying