GitHub - tonysm/importmap-laravel: Use ESM with import maps to manage modern JavaScript in Laravel without transpiling or bundling.

Introduction

Use ESM with importmap to manage modern JavaScript in Laravel without transpiling or bundling.

Inspiration

This package was inspired by the Importmap Rails gem. Some pieces of this README were copied straight from there and adapted to the Laravel version.

How does it work?

Import maps let you import JavaScript modules using logical names that map to versioned/digested files – directly from the browser. So you can build modern JavaScript applications using JavaScript libraries made for ES modules (ESM) without the need for transpiling or bundling. This frees you from needing Webpack, Yarn, npm, or any other part of the JavaScript toolchain.

With this approach, you'll ship many small JavaScript files instead of one big JavaScript file. Thanks to HTTP/2 that no longer carries a material performance penalty during the initial transport, and offers substantial benefits over the long run due to better caching dynamics. Whereas before any change to any JavaScript file included in your big bundle would invalidate the cache for the whole bundle, now only the cache for that single file is invalidated.

There's native support for import maps in Chrome/Edge 89+/Firefox 108+, and a shim available for any browser with basic ESM support. So your app will be able to work with all the evergreen browsers.

Installation

You can install the package via Composer:

composer require tonysm/importmap-laravel

The package has an install command that you may run to replace the default Laravel scaffold with one to use importmap:

php artisan importmap:install

Next, we need to add the following component to our view or layout file:

Add that between your <head> tags. The entrypoint should be the "main" file, commonly the resources/js/app.js file, which will be mapped to the app module (use the module name, not the file).

By default the x-importmap-tags component assumes your entrypoint module is app, which matches the existing resources/js/app.js file from Laravel's default scaffolding. You may want to customize the entrypoint, which you can do with the entrypoint prop:

<x-importmap-tags entrypoint="admin" />

The package will automatically map the resources/js folder to your public/js folder using Laravel's symlink feature. All you have to do after installing the package is run:

If you're using Laravel Sail, make sure you prefix that command with sail as the symlink needs to be created inside the container.

The symlink is only registered on local environments. For production, it's recommended to run the importmap:optimize command instead:

php artisan importmap:optimize

This should scan all your pinned files/folders (no URLs) and publish them to public/dist/js, adding a digest based on the file's content to the file name - so something like public/dist/js/app-123123.js, and then generate a .importmap-manifest.json file in the public/ folder. This file will get presence over your pins. If you run that by accident in development, make sure you delete that file or simply run php artisan importmap:clear, which should get rid of it. You may also want to add /public/dist to your .gitignore file, as well as *importmap-manifest.json.

Usage

In a nutshell, importmap works by giving the browser a map of where to look for your JavaScript import statements. For instance, you could pin a dependency in the routes/importmap.php file for Alpinejs like so:

<?php

use Tonysm\ImportmapLaravel\Facades\Importmap;

// Other pins...
Importmap::pin("alpinejs", to: "https://ga.jspm.io/npm:alpinejs@3.8.1/dist/module.esm.js");

Then, in your JavaScript files you can safely do:

import Alpine from 'alpinejs';

Pinning Local Files

Local pins should be added to the routes/importmap.php file manually, like so:

Importmap::pin("app", to: "/js/app.js");

This means that the app module will point to /js/app.js in the browser. This is the URI the browser will use to fetch the file, not the path to the file itself. Pins to local files assume a relative path of resources/js/ to find them.

Pinning Local Directories

Declaring all your local files can be tedious, so you may want to map an entire folder like so:

Importmap::pinAllFrom("resources/js/", to: "js/");

When we're generating the importmap JSON, we'll scan that directory looking for any .js or .jsm files inside of it and generating the correct importmap for them based on their relative location. There are a couple of interesting rules, though, something like:

Path	Module	URI
`resources/js/app.js`	`app`	`/js/app.js`
`resources/js/controllers/hello_controller.js`	`controllers/hello_controller`	`/js/controllers/hello_controller.js`
`resources/js/libs/index.js`	`libs`	`/js/libs/index.js`

If there's an index.js file in a folder, we won't get index in the module name, so we can import it like

Instead of

import libs from 'libs/index';

Pinning External Dependencies

If you depend on any external library you can use the importmap:pin command to pin it, like so:

php artisan importmap:pin alpinejs

That will add the following line to your routes/importmap.php file:

Importmap::pin("alpinejs", to: "https://ga.jspm.io/npm:alpinejs@3.8.1/dist/module.esm.js");

The pin command makes use of the jspm.io API to resolve the dependencies (and the dependencies of our dependencies), looking for ESM modules that we can pin, and resolving it to a CDN URL. We can control the CDN we want to use by specifying the --from flag like so:

php artisan importmap:pin alpinejs --from=unpkg

Which should generate a pin like so:

Importmap::pin("alpinejs", to: "https://unpkg.com/alpinejs@3.8.1/dist/module.esm.js");

It's preferred that you always pin from the same CDN, because then your browser will reuse the same SSL handshake when downloading the files (which means they will be downloaded faster).

Alternatively to using CDNs, you may prefer to vendor the libraries yourself, which you can do by using the --download flag, like so:

php artisan importmap:pin alpinejs --download

This will resolve the dependencies (and the dependencies of our dependencies) and download all the files to your resources/js/vendor folder, which you should add to your version control and maintain yourself. The pin will look like this:

Importmap::pin("alpinejs", to: "/js/vendor/alpinejs.js"); // @3.8.1

The version is added as a comment to your pin so you know which version was imported. Don't remove that as it's gonna be useful later on when you need to upgrade your dependencies.

Preloading Modules

To avoid the waterfall effect where the browser has to load one file after another before it can get to the deepest nested import, we support modulepreload links. Pinned modules can be preloaded by appending preload: true to the pin, like so:

Importmap::pinAllFrom("resources/js/", to: "js/", preload: true);
Importmap::pin("alpinejs", to: "https://unpkg.com/alpinejs@3.8.1/dist/module.esm.js", preload: true); // @3.8.1

Which will add the correct links tags to your head tag in the HTML document, like so:

<link rel="modulepreload" href="https://unpkg.com/alpinejs@3.8.1/dist/module.esm.js">

Dependency Maintenance Commands

Maintaining a healthy dependency list can be tricky. Here are a couple of commands to help you with this task.

Outdated Dependencies

To keep your dependencies up-to-date, make sure you run the importmap:outdated command from time to time:

php artisan importmap:outdated

This command will scan your config/importmap.php file, find your current versions, then use the NPM registry API to look for the latest version of the packages you're using. It also handles locally served vendor libs that you added using the --download flag from the importmap:pin command.

Auditing Dependencies

If you want a security audit on your dependencies to see if you're using a version that's been breached, run the importmap:audit command from time to time. Better yet, add that command to your CI build:

php artisan importmap:audit

This will also scan your config/importmap.php file, find your current versions, then use the NPM registry API to look for vulnerabilities in your packages. It also handles locally served vendor libs that you added using the --download flag from the importmap:pin command.

Turning Off The Shim

Under certain circumstances, like running browser tests using chromedriver under CI (which may be resource constrained and trigger errors in certain cases), you may want to explicitly turn off including the shim. You can do this by setting the importmap.use_shim config to false. You may also set it to something like 'use_shim' => ! env('CI').

Known Problems

Browser Console Errors

While import maps are native in Chrome, Edge, and Firefox, they need a shim in other browsers that'll produce a JavaScript console error like TypeError: Module specifier, 'app' does not start with "/", "./", or "../".. This error is normal and does not have any user-facing consequences.

In Firefox, when opening the browser console, the asm.js module lexer build will run in unoptimized mode due to the debugger attaching. This gives a warning message "asm.js type error: Disabled because no suitable wasm compiler is available" which is as expected. When the console is closed again, the asm.js optimizations are fully applied, and this can even be verified with the console open by disabling the debugger in about:config and reloading the page.

On React's JSX and Vue's SFC

It's possible to use both React and Vue with importmaps but, unfortunately, you would have to use those without the power of JSX or SFC. That's because those file types need a compilation/transpilation step where they are converted to something the browser can understand. There are alternative ways to use both these libraries, but I should say that these are not "common" ways in their communities. You may use React with HTM. And you can use Vue just fine without SFC, the only difference is that your templates would be in Blade files, not a SFC file.

Process ENV Configs

You may be used to having a couple process.env.MIX_* lines in your JS files here and there. The way this works is Webpack would replace at build time your calls to process.env with the values it had during the build. Since we don't have a "build time" anymore, this won't work. Instead, you should add <meta> tags to your layout file with anything that you want to make available to your JavaScript files and use document.head.querySelector('meta[name=my-config]').content instead of relying on the process.env.

Consider using something like current.js to easily consume your <meta> configs using a globally available Current object.

Absortio

GitHub - tonysm/importmap-laravel: Use ESM with import maps to manage modern JavaScript in Laravel without transpiling or bundling.

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