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Nov 9th, 2023

Myth: JS imports need a Build System

Written by weaverryan

Myth: JS imports need a Build System

Read the entire series about LAST Stack:

And look out for the 30 Days with Last Stack tutorial.

When I was a youngster (back when we kids had to walk uphill both ways to school through snow) JavaScript thrived on global variables. We added a script tag to jQuery, then, bam! We could run around and use $ as recklessly as our heart desired. It was the best of times... it was the weirdest of times.

<script src=""></script>
    $(document).ready(function() {
        #('body').innerHTML('A simpler time...');

Then Node invented require and module.exports. This gave us the concept of "modules": instead of setting & relying on global variables, we could explicitly export & import code from one file to another. Nice!

Eventually (way back in 2015!), the JavaScript community standardized modules with the import and export keywords. And suddenly, JavaScript started to look like a real programming language.

The Rise of Bundlers

There was just one problem: browsers didn't understand import! This ushered in the era of bundlers: tools like Webpack that would crawl through your JavaScript files, find the import statements and combine everything into a final set of files that browsers could understand - i.e. files that did not have import & export.

The Rise of Browsers

But, unless you're building an SPA with a frontend framework, the era of bundlers is over! Browsers do now understand import and export natively, and have for a while.

Let's try it right now! Seriously! Find a project, open base.html.twig or any file, paste anywhere... then refresh. I'll wait:

<script type="module">
    import { cowthink } from '';

    console.log(cowthink('I\'d rather eat grass than keep bundling... though I do ❤️ grass...'));

That's right, that cow did just give you its opinion on bundlers... and grass. But the point is: this "just works". If importing from a URL looks weird to you - that's ok. We don't do this in practice thanks to "importmaps"... but that's a topic for another day (and something that AssetMapper handles for you).

The Rise of AssetMapper

So then... do we still need bundlers? Let's find out with this handy questionnaire:

1) Do you need to support IE 11? If yes -> then you need a bundler. And, you should chat with your client about this - even Microsoft dropped IE 11 support more than 2 years ago and 0.37% of users are still using it as of Nov 2023). Don't be a browser "hoarder". It's ok to let go.

2) Are you building an SPA with a frontend framework? If yes -> then you need a bundler and you should use the tools that come with that framework.

3) Else -> you don't need a bundler! 🚀

This means we can serve our unbundled, source JavaScript files directly. And that's what AssetMapper is all about: it lets you code like "normal" and serves up your raw, individual files (with versioned filenames for caching & a few other goodies).

In the next post, I'll talk about performance, why we don't combine files, HTTP/2 and caching.


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