A Webpack Survival Guide for Rails Developers

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LOOK BEFORE YOU import ROSS KAFFENBERGER @rossta WEBPACK FOR RAILS DEVELOPERS SURV I VA L G UI D E A

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ROSS KAFFENBERGER @rossta WEBPACK WIT HOUT LOSIN G YOUR HAIR HOW TO

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ROSS

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R O S S uby pen ource oftware

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ROSS conf

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learnzillion.com/careers

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I really mean:

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#poop

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#poop

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Last year…

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3 scenarios

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3 scenarios 6 problems

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3 scenarios 6 problems 7 survival tips

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First…

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Sprockets Webpack

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Sprockets Webpack Packaging assets for the browser

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Sprockets Webpack

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Sprockets Webpack File concatenation

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Sprockets Webpack File concatenation Static module bundling

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Better dev tools

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Better dev tools Better dependency management

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Better dev tools Better dependency management Huge ecosystem

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Better dev tools Better dependency management Huge ecosystem ES6*

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Better dev tools Better dependency management Huge ecosystem ES6* Dynamic code splitting

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https://webpack.wtf

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•Webpack WTF? •screenshots •quotes

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Webpack tutorials SurviveJS Webpack Book - Juho Vepsäläinen survivejs.com/webpack Webpack Learning Academy - Sean Thomas Larkin webpack.academy Webpack from Nothing - David Bryant Copeland what-problem-does-it-solve.com/webpack/index.html

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SURVIVAL SCENARIOS

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SURVIVAL SCENARIOS ORGANIZING CODE

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SURVIVAL SCENARIOS ORGANIZING CODE TAMING DEPENDENCIES

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SURVIVAL SCENARIOS ORGANIZING CODE TAMING DEPENDENCIES PREDICTABLE CACHING

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SURVIVAL SCENARIOS >ORGANIZING CODE TAMING DEPENDENCIES PREDICTABLE CACHING

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Organizing code Directory structure

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sprockets

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sprockets Organizing code

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sprockets Organizing code app/ assets/ javascripts/ application.js admin.js my_function.js my_module.js components/ component_a.js component_b.js

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sprockets Organizing code app/ assets/ javascripts/ application.js admin.js my_function.js my_module.js components/ component_a.js component_b.js public/ assets/ javascripts/ application-abc123...js admin-def456...jss

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webpacker+

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webpacker+ Organizing code app/ assets/ javascripts/ application.js admin.js my_function.js my_module.js components/ component_a.js component_b.js

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webpacker+ app/ webpacker+ assets/ javascripts/ my_function.js my_module.js components/ component_a.js component_b.js application.js admin.js ... javascript/ packs/ Organizing code

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webpacker+ app/ webpacker+ entry assets/ javascripts/ my_function.js my_module.js components/ component_a.js component_b.js application.js admin.js ... javascript/ packs/ Organizing code

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webpacker+ app/ public/ assets/ javascripts/ ... packs/ application-abc123...js admin-def456...js webpacker+ entry assets/ javascripts/ my_function.js my_module.js components/ component_a.js component_b.js application.js admin.js ... javascript/ packs/ Organizing code

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webpacker+ app/ public/ assets/ javascripts/ ... packs/ application-abc123...js admin-def456...js webpacker+ output entry assets/ javascripts/ my_function.js my_module.js components/ component_a.js component_b.js application.js admin.js ... javascript/ packs/ Organizing code

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webpacker+ app/ public/ assets/ javascripts/ ... packs/ application-abc123...js admin-def456...js webpacker+ output entry “packs” auto-configured assets/ javascripts/ my_function.js my_module.js components/ component_a.js component_b.js application.js admin.js ... javascript/ packs/ Organizing code

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Organizing code

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Organizing code

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Organizing code

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Organizing code

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Organizing code

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webpacker+ app/ webpacker+ assets/ javascripts/ my_function.js my_module.js components/ component_a.js component_b.js application.js admin.js ... javascript/ packs/ Organizing code

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Organizing code webpacker+ app/ assets/ javascripts/ my_function.js my_module.js components/ component_a.js component_b.js application.js admin.js ... javascript/ packs/

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Organizing code webpacker+ app/ assets/ javascripts/ my_function.js my_module.js components/ component_a.js component_b.js application.js admin.js ... javascript/ packs/

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Organizing code webpacker+ $ bin/webpack

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Organizing code webpacker+ $ bin/webpack

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Organizing code webpacker+ $ bin/webpack

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Organizing code webpacker+ $ bin/webpack

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Quick fix Keep entry js separate

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webpacker+ app/ assets/ javascripts/ ... javascript/ my_function.js my_module.js components/ component_a.js component_b.js packs/ application.js admin.js public/ assets/ javascripts/ ... packs/ application-abc123...js admin-def456...js Organizing code webpacker+ ✅

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Organizing code webpacker+

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Organizing code webpacker+

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Survival tip #1 Don’t assume Webpacker conventions match Sprockets conventions

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Organizing code How to “require_tree”?

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sprockets Organizing code // app/assets/javascripts/application.js //= require_tree ./some_directory

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webpacker+ Organizing code // app/javascript/packs/application.js import 'some_directory'

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webpacker+ require.context Organizing code // app/javascript/packs/application.js import 'some_directory'

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webpacker+ require.context Organizing code // app/javascript/some_directory/index.js const requireModule = require.context('.', true, /\.js$/) // app/javascript/packs/application.js import 'some_directory' requireModule.keys() // ['./module_a.js', ‘./module_b.js', ...] .filter(filename => filename !== './index.js') .forEach(requireModule)

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webpacker+ Organizing code // app/javascript/packs/application.js import { SomeComponent } from 'some_directory'

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webpacker+ Organizing code // app/javascript/some_directory/index.js import camelCase from 'lodash/camelCase' const requireModule = require.context('.', false, /\.js$/) const modules = {} requireModule.keys().forEach(fileName => { if (fileName === './index.js') return const moduleName = camelCase( fileName.replace(/(\.\/|\.js)/g, '') ) modules[moduleName] = requireModule(fileName) }) export default modules

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Survival tip #2 In Webpack, accept control > friendliness

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SURVIVAL SCENARIOS ORGANIZING CODE✔ >TAMING DEPENDENCIES PREDICTABLE CACHING

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Taming dependencies Code splitting

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sprockets Taming dependencies app/ assets/ javascripts/ application.js vendor.js sprockets

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sprockets Taming dependencies app/ assets/ javascripts/ application.js vendor.js sprockets // app/views/layouts/application.html.erb <%= javascript_include_tag "vendor" %> <%= javascript_include_tag "application" %>

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sprockets Taming dependencies app/ assets/ javascripts/ application.js vendor.js sprockets // app/assets/javascripts/vendor.js //= require jquery-rails // app/views/layouts/application.html.erb <%= javascript_include_tag "vendor" %> <%= javascript_include_tag "application" %>

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sprockets Taming dependencies app/ assets/ javascripts/ application.js vendor.js sprockets // app/assets/javascripts/vendor.js //= require jquery-rails // app/assets/javascripts/application.js //= require chosen-js //= require slick-carousel // app/views/layouts/application.html.erb <%= javascript_include_tag "vendor" %> <%= javascript_include_tag "application" %>

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sprockets Taming dependencies app/ assets/ javascripts/ application.js vendor.js sprockets // app/assets/javascripts/vendor.js //= require jquery-rails // app/assets/javascripts/application.js //= require chosen-js //= require slick-carousel manual code splitting // app/views/layouts/application.html.erb <%= javascript_include_tag "vendor" %> <%= javascript_include_tag "application" %>

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webpacker+ Taming dependencies app/ javascript/ packs/ application.js vendor.js

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webpacker+ Taming dependencies app/ javascript/ packs/ application.js vendor.js // app/views/layouts/application.html.erb <%= javascript_pack_tag "vendor" %> <%= javascript_pack_tag "application" %>

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webpacker+ Taming dependencies app/ javascript/ packs/ application.js vendor.js // app/javascript/packs/vendor.js import 'jquery' // app/views/layouts/application.html.erb <%= javascript_pack_tag "vendor" %> <%= javascript_pack_tag "application" %>

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webpacker+ Taming dependencies app/ javascript/ packs/ application.js vendor.js // app/javascript/packs/vendor.js import 'jquery' // app/javascript/packs/application.js import 'chosen-js' import 'slick-carousel' // app/views/layouts/application.html.erb <%= javascript_pack_tag "vendor" %> <%= javascript_pack_tag "application" %>

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webpacker+ Taming dependencies // app/javascript/packs/vendor.js import 'jquery'

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webpacker+ Taming dependencies // app/javascript/packs/application.js // app/javascript/packs/vendor.js import 'jquery'

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webpacker+ Taming dependencies // app/javascript/packs/application.js // app/javascript/packs/application.js import 'chosen-js' // app/javascript/packs/vendor.js import 'jquery'

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webpacker+ > typeof $.fn.chosen “function" Taming dependencies // app/javascript/packs/application.js // app/javascript/packs/application.js import 'chosen-js' // app/javascript/packs/vendor.js import 'jquery'

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webpacker+ > typeof $.fn.chosen “function" > typeof $.fn.chosen “function" > typeof $.fn.slick "function" Taming dependencies // app/javascript/packs/application.js // app/javascript/packs/application.js import 'chosen-js' // app/javascript/packs/application.js import 'chosen-js' import 'slick-carousel' // app/javascript/packs/vendor.js import 'jquery'

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webpacker+ Taming dependencies $ yarn add webpack-bundle-analyzer

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webpacker+ Taming dependencies // config/webpack/development.js const environment = require('./environment') const BundleAnalyzerPlugin = require(‘webpack-bundle-analyzer').BundleAnalyzerPlugin environment.plugins.append( 'BundleAnalyzerPlugin', new BundleAnalyzerPlugin() ) $ yarn add webpack-bundle-analyzer

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webpacker+ Taming dependencies

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webpacker+ Taming dependencies

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webpacker+ Taming dependencies

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webpacker+ Taming dependencies

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webpacker+ Taming dependencies

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webpacker+ Taming dependencies import 'chosen-js'

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webpacker+ (function() { // ... $ = jQuery $.fn.extend({ chosen: function(options) { // ... } }) // ... }).call(this) Taming dependencies import 'chosen-js'

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webpacker+ (function() { // ... $ = jQuery $.fn.extend({ chosen: function(options) { // ... } }) // ... }).call(this) Taming dependencies import 'chosen-js' assumes “jQuery” in global scope

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webpacker+ Taming dependencies import 'slick-carousel'

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webpacker+ Taming dependencies (function(factory) { if (typeof exports !== 'undefined') { module.exports = factory(require('jquery')) } else if (typeof define === 'function' && define.amd) { define(['jquery'], factory) } else { factory(jQuery) } })(function($) { // library code }) import 'slick-carousel'

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webpacker+ Taming dependencies

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Quick fix Code splitting? Let Webpack do the work

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webpacker+ Taming dependencies // config/webpack/environment.js const webpack = require('webpack') const { environment } = require('@rails/webpacker') environment.plugins.append( 'CommonsChunkVendor', new webpack.optimize.CommonsChunkPlugin({ name: 'vendor', }) )

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webpacker+ Taming dependencies

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webpacker+ Taming dependencies ✅

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Survival tip #3 Know your dependencies

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Taming dependencies Module shimming

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Taming dependencies (Applying transformations)

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webpacker+ Taming dependencies

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webpacker+ Taming dependencies $ yarn add expose-loader

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webpacker+ Taming dependencies // config/webpack/environment.js const { environment } = require('@rails/webpacker') environment.loaders.append('jquery', { test: require.resolve('jquery'), use: [{ loader: 'expose-loader', options: '$', }], }) $ yarn add expose-loader

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webpacker+ (function() { // ... $ = jQuery $.fn.extend({ chosen: function(options) { // ... } }) // ... }).call(this) Taming dependencies import 'chosen-js'

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webpacker+ (function() { // ... $ = jQuery $.fn.extend({ chosen: function(options) { // ... } }) // ... }).call(this) Taming dependencies import 'chosen-js'

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webpacker+ Taming dependencies $ yarn add imports-loader

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webpacker+ // config/webpack/environment.js const { environment } = require('@rails/webpacker') environment.loaders.append('chosen-js', { test: require.resolve('chosen-js'), use: [{ loader: 'imports-loader', options: 'jQuery=jquery,$=jquery,this=>window', }] }) Taming dependencies $ yarn add imports-loader

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Survival tip #4 Legacy dependencies? fix or fire

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SURVIVAL SCENARIOS ORGANIZING CODE✔ TAMING DEPENDENCIES✔ >PREDICTABLE CACHING

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Predictable caching Fingerprints

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webpacker+ Predictable caching

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webpacker+ Predictable caching

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webpacker+ Predictable caching // app/javascript/packs/application.js import myFunction from 'my_function' myFunction()

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webpacker+ Predictable caching // app/javascript/packs/application.js import myFunction from 'my_function' myFunction()

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webpacker+ new dependency Predictable caching // app/javascript/packs/application.js import myFunction from 'my_function' import myModule from 'my_module' myFunction() console.log('MyModule', myModule)

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webpacker+ Predictable caching // app/javascript/packs/application.js import myFunction from 'my_function' import myModule from 'my_module' myFunction() console.log('MyModule', myModule) // app/javascript/my_module.js export default { name: 'MyModule', render() { return '

MyModule

' }, }

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webpacker+ Predictable caching // app/javascript/packs/application.js import myFunction from 'my_function' import myModule from 'my_module' myFunction() console.log('MyModule', myModule)

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webpacker+ Predictable caching // app/javascript/packs/application.js import myFunction from 'my_function' import myModule from 'my_module' myFunction() console.log('MyModule', myModule)

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webpacker+ application-6abd5649df983f5ce62c.js vendor-1f142b407ddab8388a61.js before… Predictable caching

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webpacker+ application-6abd5649df983f5ce62c.js vendor-1f142b407ddab8388a61.js application-3f225177efeb4e965518.js vendor-0434e3b09308803b8702.js before… after… Predictable caching

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webpacker+ application-6abd5649df983f5ce62c.js vendor-1f142b407ddab8388a61.js application-6abd5649df983f5ce62c.js vendor-1f142b407ddab8388a61.js application-3f225177efeb4e965518.js vendor-0434e3b09308803b8702.js application-3f225177efeb4e965518.js vendor-0434e3b09308803b8702.js application-3f225177efeb4e965518.js vendor-0434e3b09308803b8702.js application-6abd5649df983f5ce62c.js vendor-1f142b407ddab8388a61.js before… after… Surprise! Both bundles changed! Predictable caching

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webpacker+ Anatomy of a bundle .js A brief cartoon interlude…

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webpacker+ Anatomy of a bundle .js Entry

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webpacker+ Anatomy of a bundle .js .js .js .js .jpg .css .js Entry

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webpacker+ Anatomy of a bundle

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webpacker+ Anatomy of a bundle

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webpacker+ Anatomy of a bundle

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webpacker+ Runtime typical-bundle.js Anatomy of a bundle

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webpacker+ Runtime typical-bundle.js 0 1 2 3 4 5 6 Anatomy of a bundle

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webpacker+ Anatomy of a bundle vendor.js application.js

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webpacker+ vendor.js 0 1 2 3 4 application.js 5 6 7 8 Anatomy of a bundle

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webpacker+ vendor.js 0 1 2 3 4 application.js 5 6 7 8 9 Anatomy of a bundle

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webpacker+ vendor.js 0 1 2 3 4 application.js 5 6 7 8 9 Anatomy of a bundle

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Quick fix More configuration (yay)

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webpacker+ // config/webpack/environment.js const webpack = require('webpack') const { environment } = require('@rails/webpacker') environment.plugins.append( 'CommonsChunkVendor', new webpack.optimize.CommonsChunkPlugin({ name: 'vendor', }) ) Predictable caching

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webpacker+ // config/webpack/environment.js … continued Predictable caching

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webpacker+ // config/webpack/environment.js … continued Predictable caching // config/webpack/environment.js … continued environment.plugins.append( 'CommonsChunkManifest', new webpack.optimize.CommonsChunkPlugin({ name: 'runtime', minChunks: Infinity, }), ) extract the runtime into its own bundle

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webpacker+ vendor.js 0 1 2 3 4 application.js 5 6 7 8 Anatomy of a bundle

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webpacker+ vendor.js FA C1 3D A6 33 application.js 2F EC 4B D8 Anatomy of a bundle runtime.js

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Survival tip #5 Understand the runtime

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Predictable caching Asychronous bundles

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webpacker+ import $ from 'jquery' $('.pdf-canvas').each(() => { const url = $(this).data('url') Predictable caching PDFJS.getDocument(url).then(pdf => { // ... render pdf data to canvas }) }) import PDFJS from 'pdfjs/webpack'

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webpacker+ Predictable caching import $ from 'jquery' $('.pdf-canvas').each(() => { const url = $(this).data('url') PDFJS.getDocument(url).then(pdf => { // ... render pdf data to canvas }) import('pdfjs/webpack').then((PDFJS) => { }) })

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webpacker+ Predictable caching import( 'pdfjs/webpack').then(…)

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webpacker+ Predictable caching import( 'pdfjs/webpack').then(…) /* webpackChunkName: "pdfjs" */

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webpacker+ Predictable caching import( Use a “chunk name” for consistent bundle caching 'pdfjs/webpack').then(…) /* webpackChunkName: "pdfjs" */

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webpacker+ Predictable caching import( Use a “chunk name” for consistent bundle caching 'pdfjs/webpack').then(…) /* webpackChunkName: "pdfjs" */

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webpacker+ Predictable caching import( Use a “chunk name” for consistent bundle caching 'pdfjs/webpack').then(…) /* webpackChunkName: "pdfjs" */

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Survival tip #6 Prioritize async bundles

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SURVIVAL SCENARIOS ORGANIZING CODE✔ TAMING DEPENDENCIES✔ PREDICTABLE CACHING✔