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Jaydson Gomes
Posted by
Tue Oct 28 2014 12:49:54 GMT+0000 (UTC)

ES6 modules today with 6to5

I've posted the image below on Twitter showing how happy I was.
It's great what transpilers can do. In JavaScript's World it's like a time machine we can forward to the near future of awesomeness ES6 will bring.
In this tutorial we'll show how to start writing ES6 modules today, using the awesome 6to5.

modules today with 6to5

First step

If you are not familiar with ES6 modules, please check JSModules.io for an brief introduction.
Also, I recommend you to read @jcemer's article A new syntax for modules in ES6, here in ES6Rocks, that covers a lot of more cool stuff around modules in JavaScript.
For this tutorial we'll use the 6to5 transpiler.
Basically, "6to5 turns ES6 code into vanilla ES5, so you can use ES6 features today".
6to5 has some advantages over other transpilers, here are the main features:
Readable: formatting is retained if possible so your generated code is as similar as possible.
Extensible: with a large range of plugins and browser support.
Lossless: source map support so you can debug your compiled code with ease.
Compact: maps directly to the equivalent ES5 with no runtime.

Writing modules

Let's start writing modules!
Our application will do nothing but logs, but the main idea here is make you understand how modules works and how to implement ES6 modules right now in your applications.
Our basic app structure:

├── Gruntfile.js
├── package.json
└── src
    ├── app.js
    ├── modules
    │   ├── bar.js
    │   ├── baz.js
    │   └── foo.js
    └── sample
        └── index.html

app.js is the main file, and inside the modules directory we'll store all our modules.
Take a look at app.js:

import foo from "./modules/foo";
import bar from "./modules/bar";

console.log('From module foo >>> ', foo);
console.log('From module bar >>> ', bar);

It's pretty simple. The code above does exactly what it looks like.
We're importing module foo and module bar, and then logging the content of each one.
To be more clear, let's look at each module:

// foo
let foo = 'foo';

export default foo;
// bar
let bar = 'bar';

export default bar;

In both modules we're just exporting the strings 'foo' and 'bar'.
When we import the module, our variable has the data we exported.
Then, foo in import foo from "foo" has the data 'foo' we exported in export default foo.
You can also export objects, classes, functions, etc.
Now, you can start to hack this simple example and write your own modules.


As you may know, ES6 modules are not supported yet by any browser nor Node.js.
The only way to write ES6 modules today is using a transpiler.
As I mentioned before, I'm using 6to5, that does exactly what we want.
The task runner we chose was Grunt, and we'll use @sindresorhus's grunt-6to5.

npm install grunt-cli -g
npm install grunt --save-dev
npm install grunt-6to5 --save-dev

Our Gruntfile will look like this:

    '6to5': {
        options: {
            modules: 'common'

        build: {
            files: [{
                expand: true,
                cwd: 'src/',
                src: ['**/*.js'],
                dest: 'dist/',

A pretty simple configuration and we're almost there.
The 6to5 task just runs 6to5 against the src dir and transpiles the code to the dist directory.
Note the modules: 'common' option. This tells 6to5 to transpile our modules to ES5 CommonJS modules style.
6to5 also supports AMD which is great, because we can integrate ES6 modules to our current environment, independent of our legacy/current modules style choice.

To test it in the browser, I made a copy task that just copies the sample/index.html file to our dist directory.
The HTML file looks like this:

<!doctype html>
<html lang="en">
    <meta charset="UTF-8">
    <title>ES6 modules 6to5</title>
    <script src="//[cdnjs URL]/require.min.js"></script>

Look at the code above, we put RequireJS as our AMD library and then just require the app.
For this test to work, you'll need to set the option modules: amd.


Now we have everything set, you can just run grunt.
If you missed something, you can clone the repo es6-modules-today-with-6to5, and run npm install.

Remember, the Grunt task will generate a dist folder with the transpiled code.
So, if you choose to transpile ES6 modules to CommonJS, you can test the app with node:

node dist/app.js

Running with node

If you choose AMD, just serve the dist folder, and access the page index.html.


With this simple tutorial you can see how easy it is to setup an ES6 environment to work with modules.
6to5 is an excelent painless tool you can use today to transpile future ES6 code to current ES5 code.
Go ahead and fork the repo es6-modules-today-with-6to5, submit issues, questions or pull-requests.
Comments are welcome :)

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