Require Outside Libraries

When you use Webpack, the hardest thing is that you need to start thinking about your JavaScript differently. You need to stop thinking about global variables, and start thinking about how you can code correctly. It's not as easy as it sounds: we've been using global variables in JavaScript... well... forever!

For example, in RepLogApp.js, we created this self-executing function to give our code a little bit of isolation:

215 lines public/assets/js/RepLogApp.js
... lines 1 - 4
(function(window, $, Routing, swal) {
... lines 6 - 213
})(window, jQuery, Routing, swal);

That part isn't too important. But at the bottom, we are relying on there to be a global jQuery variable. It just must exist, or else everything will explode! On top, this becomes a $ variable in the function.

Open the base layout file - base.html.twig. The only reason our code works is that, at the bottom, yep! We have a script tag for jQuery, which adds a global jQuery variable:

110 lines templates/base.html.twig
... lines 1 - 98
{% block javascripts %}
<script src="" integrity="sha256-hVVnYaiADRTO2PzUGmuLJr8BLUSjGIZsDYGmIJLv2b8=" crossorigin="anonymous"></script>
... lines 101 - 105
{% endblock %}
... lines 107 - 110

And this is the process we've used for years: add a script tag for a JS library, then reference its global variable everywhere else.

I hate this! In RepLogApp.js, I just have to hope that jQuery was included correctly. That's madness, and it needs to stop. So, from now on, we have a new philosophy: if we need a variable in a file - like $ - then we need to require it in the same way that we are requiring Helper.

The only difference is that jQuery is a third-party library. Well... in PHP, we would use Composer to install third-party libraries. And... yea! In JavaScript, we can use Yarn to do the same thing!

Installing jQuery via Yarn

Check this out: open a third terminal tab - we're getting greedy! Then run:

yarn add jquery --dev

Yep! We can use yarn to download front-end libraries! Oh, and you can search for package names on or

This downloads jquery into the node_modules/ directory and adds it to package.json:

8 lines package.json
"devDependencies": {
... line 3
"jquery": "^3.3.1",
... line 5

Requiring jQuery

So... how do we require it? Oh, it's awesome: const $ = require('jquery'):

216 lines public/assets/js/RepLogApp.js
... lines 1 - 2
const Helper = require('./RepLogHelper');
const $ = require('jquery');
... lines 5 - 216

That's it! When a require path does not start with a ., Webpack knows to look for a package in node_modules/ with that name.

And now that we are properly importing the $ variable - yay us - remove $ and jQuery from the self-executing function:

216 lines public/assets/js/RepLogApp.js
... lines 1 - 3
const $ = require('jquery');
(function(window, Routing, swal) {
... lines 7 - 214
})(window, Routing, swal);

Yep, when we use the $ variable below, it is no longer dependent on any global jQuery variable! Responsible coding for the win!

But... does it work? Try it! Go back to our site and refresh! It does! That's because, back on the terminal, if you run:

ls -la public/build

... yep! Our rep_log.js file now has jQuery inside of it - you know because it's now 300kb! Don't worry, we'll talk about optimizations later.

But the point is this: all we need to do is require the libraries we need, and Webpack takes care of the rest!

Installing & Using SweetAlert2

Let's require one more outside package. Search for "swal". We're using a really cool library called SweetAlert to bring up the delete dialog. But... the only reason this works is that, in the template, we're including a script tag for it:

67 lines templates/lift/index.html.twig
... lines 1 - 47
{% block stylesheets %}
... lines 49 - 50
<link rel="stylesheet" href="" />
{% endblock %}
... line 53
{% block javascripts %}
... lines 55 - 56
<script src=""></script>
... lines 58 - 65
{% endblock %}

Boo! Let's refactor this to require that library properly.

If you search for this package, you'll find out that it's called sweetalert2. Let's install it:

yarn add sweetalert2 --dev

This time, delete the script tag entirely. We can't remove the jQuery script tag yet because we're still using the global variable in a few places. But, we'll fix that soon.

Then, in RepLogApp.js, remove the argument from the self-executing function: that global variable doesn't even exist anymore!

217 lines public/assets/js/RepLogApp.js
... lines 1 - 6
(function(window, Routing) {
... lines 8 - 215
})(window, Routing);

To prove it, refresh! Awesome!

swal is not defined

To get it back, add const swal = require('sweetalert2');:

217 lines public/assets/js/RepLogApp.js
... lines 1 - 4
const swal = require('sweetalert2');
(function(window, Routing) {
... lines 8 - 215
})(window, Routing);

As soon as we save this, Webpack recompiles, we refresh and... it works! Yes! We can use any outside library by running one command and adding one require line.

Let's use our new unstoppable skills to refactor our code into re-usable components.

Leave a comment!

  • 2018-04-23 Diego Aguiar

    Hey JAVroegop

    Nice tip, thanks for sharing it :)

  • 2018-04-23 JAVroegop

    If you ever get a warning from Yarn like this:

    An unexpected error occurred: "EPERM: operation not permitted, unlink '.....\\node_modules\\.bin\\encore'"

    Before you try to install jquery, please stop encore. I spent quite a while figuring out why yarn couldn't delete node_modules/.bin/encore... on my Windows 10 machine. *Doh!*