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Ok, so do you love ES2015 yet? Man, I sure do. So... let's go use it immediately on our site! Oh wait.... didn't I mention that its features aren't supported by all browsers? Whoops. Yea, the latest version of Chrome supports everything... but if some of our users have older browsers, does this mean we can't use ES2015?

npm and yarn: Package Manager Battle!

Nope! You can! Thanks to an amazing tool called Babel. But before we talk about it, we need to do a little bit of installation. In the Node.js world, the package manager is called npm, and because you already installed Node, you already have it!

But wait! There's a disturbance in the Node.js package manager force. Yes, there is another... package manager... called Yarn! It's sort of a competitor to npm, but they work almost identically. For example, in PHP, we have a composer.json file. In Node, we will have a package.json... and you can use either npm or yarn to read it.

In other words,... you can use npm or yarn: they basically do the same thing. You could even have some people on your team using npm, and others using yarn.

We're going to use Yarn... because it's a bit more sophisticated. But, that means you need to install it! I'm on a Mac, so I already installed it via Brew. Check Yarn's Docs for your install details.

Creating a package.json

To use Yarn, we need a package.json file... which we don't have yet! No worries, to create one, run:

yarn init

It'll ask a bunch of questions - none are too important - and you can always update your new package.json file by hand later:

9 lines package.json
{
"name": "javascript",
"version": "1.0.0",
"main": "index.js",
"repository": "git@github.com:knpuniversity/javascript.git",
"author": "Ryan Weaver <ryan@thatsquality.com>",
"license": "MIT"
}

Awesome!

Installing Babel

Ok, the wonderful tool that will fix all of our browser compatibility problems with ES2015 is called Babel. Google for it to find babeljs.io.

In a nut shell, Babel reads new JavaScript code, i.e. ES2015 code, and recompiles it to old JavaScript so that all browsers can understand it. Yea, it literally reads source code and converts it to different source code. It's wild!

Go to Setup. In our case, to see how it works, we're going to use the CLI, which means we will run Babel from the command line. To install Babel CLI, it wants us to run npm install --save-dev babel-cli.

But don't do it! Since we're using Yarn, run:

yarn add babel-cli --dev

That does the same thing, but with more exciting output!

This made a few changes to our project. Most importantly, it added this devDependencies section to package.json with babel-cli inside:

12 lines package.json
{
... lines 2 - 7
"devDependencies": {
"babel-cli": "^6.22.2"
}
}

It also created a yarn.lock file: which works like composer.lock. And finally, the command added a new node_modules/ directory, where it downloaded babel-cli and all of its friends, um, dependencies. That is the vendor/ directory for Node.

Open up your .gitignore file. At the bottom, let's ignore /node_modules/:

18 lines .gitignore
... lines 1 - 16
/node_modules

We don't need to commit that directory because - thanks to the package.json and yarn.lock files - anyone else can run yarn install to download everything they need.

Okay, enough setup! Let's use Babel!

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