Half Stack Fest: Webpack

The modern JS developer's workflow

The modern developer's webpack workflow

1. Google: "how to do X in webpack"

3. Copy and paste

4. It works, for now

5. But then you need to tweak it

Boilerplates are great, once you know the tool

It doesn't have to be like this

Firstly: do you actually need webpack?

Glen Madern: https://frontend.center/

What is webpack?

"An ahead of time compiler for the browser"

webpack does what the browser would do if given your
app: » find all images in your CSS and download them » parse your JavaScript dependencies and download them » parse all CSS for imports and download them

webpack can do this right at the beginning And create
a more optimised bundle, saving the browser (and user) time

webpack is not just for JavaScript

webpack Terminology to tell your friends

A module Any file that your application uses. Not just
JavaScript. CSS, images, text files, anything.

Chunk A file, or a group of files that webpack
has squashed together

Entry point A file webpack will search from to find
dependencies and modules

A loader A function that takes a file's source and
transforms it to return a new source file

Let's do it

npm init -y PSA: Don't install things globally!

npm install --save-dev webpack@2.1.0-beta.26 Run locally with ./node_modules/.bin/webpack (Or add
./node_modules/.bin to your $PATH)

index.html <!DOCTYPE html> <html> <head><title>Github</title></head> <body><script src="dist/main.js"></script></body> </html>

src/main.js fetch('https://api.github.com/users/jackfranklin') .then(function(d) { return d.json() }) .then(function(data) { console.log('Got
github data', data) })

Configuring webpack » Where should webpack start looking? » Where
should it output to?

webpack.conﬁg.js var path = require('path') module.exports = { // where
should it look? entry: path.resolve('src', 'main.js'), // where should it output to? output: { path: path.resolve(__dirname, 'dist'), ﬁlename: 'main.js', publicPath: '/dist/' } }

run webpack Hash: c09c87fc891968a374a6 Version: webpack 2.1.0-beta.26 Time: 70ms Asset
Size Chunks Chunk Names main.js 2.63 kB 0 [emitted] main [0] ./src/main.js 194 bytes {0} [built]

Watching for changes webpack --watch "scripts": { "build:dev": "webpack --watch"
}

webpack is watching the ﬁles… Hash: c09c87fc891968a374a6 Version: webpack 2.1.0-beta.26
Time: 103ms Asset Size Chunks Chunk Names main.js 2.63 kB 0 [emitted] main [0] ./src/main.js 194 bytes {0} [built] Hash: d9aad0a1ca8f706975ad Version: webpack 2.1.0-beta.26 Time: 11ms Asset Size Chunks Chunk Names main.js 2.6 kB 0 [emitted] main [0] ./src/main.js 163 bytes {0} [built]

Refreshing is so much effort npm install --save-dev webpack-dev-server@v2.1.0- beta.11

webpack-dev-server Project is running at http://localhost:8080/ webpack output is served
from /dist/ Hash: 1d366a627611ba06845c Version: webpack 2.1.0-beta.26 Time: 947ms Asset Size Chunks Chunk Names main.js 247 kB 0 [emitted] main chunk {0} main.js (main) 233 kB [entry] [rendered] [0] ./~/inherits/inherits_browser.js 672 bytes {0} [built] [1] (webpack)/buildin/global.js 506 bytes {0} [built] [2] ./~/debug/browser.js 3.76 kB {0} [built] [3] ./~/process/browser.js 5.3 kB {0} [built] ...

"scripts": { "build:dev": "webpack --watch", "start": "webpack-dev-server" },

Loaders fetch('https://api.github.com/users/jackfranklin') .then(function(d) { return d.json() }) .then(function(data) { console.log('Got
github data', data) }) Would be much nicer as: const username = 'jackfranklin' fetch(`https://api.github.com/users/${username}`) .then(d => d.json()) .then(data => console.log('Got github data', data))

Babel npm install --save-dev babel-core npm install --save-dev babel-preset-es2015 npm
install --save-dev babel-loader

webpack.conﬁg.js module.exports = { entry: path.resolve('src', 'main.js'), output: { ...
}, module: { rules: [ ] } }

webpack rules Apply transformations to certain files.

{ // apply this rule to any files that end
in ".js" test: /\.js$/, // only look for files in the src directory include: path.resolve('src'), // configure the loaders for this rule use: [{ }] }

{ test: /\.js$/, include: path.resolve('src'), use: [{ // for ﬁles
that this rule applies to // run the babel-loader against them loader: 'babel-loader', // speciﬁc options for the babel loader options: { presets: ['es2015'] } }] }

src/main.js const username = 'jackfranklin' fetch(`https://api.github.com/users/${username}`) .then(d => d.json()) .then(d
=> console.log('Got Github data', d))

Restart dev server

npm install --save whatwg-fetch

Entry points entry: { main: [ 'whatwg-fetch', path.resolve('src', 'main.js') ]
},

Let's make it a bit more interactive

const form = document.getElementById('github-form') form.addEventListener('submit', e => { e.preventDefault() const
username = document.getElementById('input-box').value fetchPerson(username) })

const fetchPerson = username => fetch(`https://api.github.com/users/${username}`) .then(d => d.json()) .then(displayPerson)

const displayPerson = user => document.getElementById('results').innerHTML = ` <h1>${user.name}</h1> <h3>${user.company}</h3>
<p>${user.bio || 'No Bio :('}</p> `

Let's get some CSS in here Remember, the goal of
webpack is for it to manage all our assets, CSS included. This is weird at first but stick with me... (Also I suck at design, please forgive)

form { width: 200px; margin: 10px auto; } #results {
width: 300px; margin: 0 auto; border: 1px solid #111; background: #ddd; }

import './style.css' const username = 'jackfranklin' ...

ERROR in ./src/style.css Module parse failed: /github-app/src/style.css Unexpected token (1:5)
You may need an appropriate loader to handle this ﬁle type. | form { | width: 200px; | margin: 10px auto; @ ./src/main.js 3:0-22 @ multi main

npm install --save-dev css-loader npm install --save-dev style-loader » CSS
Loader: parses CSS files » Style Loader: dynamically inserts stylesheets into HTML

Add another rule { test: /\.css$/, include: path.resolve('src'), use: [{
loader: 'style-loader', }, { loader: 'css-loader', }] } Loaders are applied from right to left, or bottom to top

Restart webpack-dev-server

Deploying to Production

Configuring webpack differently

"scripts": { "build:dev": "webpack --watch", "build:prod": "NODE_ENV=production webpack", "start": "webpack-dev-server"
},

npm install --save-dev webpack- conﬁg-utils

var { getIfUtils, removeEmpty } = require('webpack-conﬁg-utils') var { ifProduction,
ifNotProduction } = getIfUtils(process.env.NODE_ENV || 'development') » removeEmpty: removes undeﬁned from arrays » ifProduction: returns what it's given if NODE_ENV === 'production' » ifNotProduction: returns what it's given if NODE_ENV !== 'production'

Starting point npm run build:prod - main.js: 24.9kb (All CSS
is contained within main.js and dynamically inserted)

Plugins A webpack plugin will typically work on the bundle
as a whole, rather than on individual files.

Minifying var webpack = require('webpack') ... output: { ... },
plugins: removeEmpty([ ifProduction(new webpack.optimize.UglifyJsPlugin()) ]), module: { ... }

npm run build:prod - main.js: 11.4kb

Nice, but why have the CSS injected with JavaScript? npm
install --save-dev extract-text-webpack-plugin@v2.0.0-beta.4

var ExtractTextPlugin = require('extract-text-webpack-plugin') ... plugins: removeEmpty([ ifProduction(new webpack.optimize.UglifyJsPlugin()), new
ExtractTextPlugin('style.css'), ]),

{ test: /\.css$/, include: path.resolve('src'), loader: ExtractTextPlugin.extract('css-loader'), }

Deep breaths, lots of progress! npm run build:prod - main.js:
7.46kb - style.css: 140bytes

Finally: code splitting / lazy loading

We should keep our first page load super quick »
download JS » parse JS » execute JS This takes time.

src/fetch-person.js export const fetchPerson = username => fetch(`https://api.github.com/users/${username}`) .then(d =>
d.json()) .then(displayPerson) const displayPerson = user => document.getElementById('results').innerHTML = ` <h1>${user.name}</h1> <h3>${user.company}</h3> <p>${user.bio || 'No Bio :('}</p> `

import './style.css' import { fetchPerson } from './fetch-person' const form
= document.getElementById('github-form') form.addEventListener('submit', e => { e.preventDefault() const username = document.getElementById('input-box').value fetchPerson(username) })

We only need fetchPerson if the user clicks the button

import './style.css' const form = document.getElementById('github-form') form.addEventListener('submit', e => {
e.preventDefault() const username = document.getElementById('input-box').value System.import('./fetch-person') .then(module => module.fetchPerson) .then(fetchPerson => fetchPerson(username)) })

And now we can build to production:

npm run build:prod - main.js: 8.08kb - 0.main.js: 387bytes -
style.css: 140bytes

Wait, the build went up? This is a contrived example,
because this app is tiny! You pay a small cost because webpack has code that it inserts for lazily loading modules, but if your pages are big enough you'll get still save.

No Lazy loading bundle.app.193adde67586dd61304b.js 444 kB

Lazily loading the graph component bundle.0.513a048a93c5b8f1687b.js 431 kB bundle.app.ce8bc2ebcec6edbff6a1.js 13.1
kB

400kb first load saving

Lazy loading: not a silver bullet But when you do
want it, webpack makes it easy :)

Bonus: dead code elimination webpack 2 can parse ES2015 modules,
that is: import { x } from './y' export default function foo() {...}

ES2015 module imports and exports have to be static. So
we can go through them and see which ones are used and which ones aren't needed. This means we can eliminate any code relating to ununsed exports!

src/not-used.js export const SO_NOT_USED = 'I AM NOT USED BY
ANYTHING EVER' export const SO_USED = 'I GET USED BY THINGS' src/main.js import { SO_USED } from './not-used' console.log(SO_USED)

Stop Babel converting modules Stop Babel converting: use: [{ loader:
'babel-loader', options: { presets: [['es2015', { modules: false }]] } }]

webpack 2 + ES2015 modules = smaller builds, for free!

I've barely scratched the surface.

webpack 2 » Much improved documentation & community engagement »
Improved configuration with a nicer API and automatic validation of config » Tree shaking, easier code splitting and lazy loading » More performant

Fin » Slides & code: https://github.com/jackfranklin/half-stack- webpack » webpack 2:
webpack.js.org » Me: @Jack_Franklin, javascriptplayground.com, elmplayground.com Thanks to: Glen Maddern, Sean Larkinn, Kent C Dodds

Half Stack Fest: Webpack

Half Stack Fest: Webpack

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