Production Progressive Web Apps With JavaScript Frameworks

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Production PWAs With JavaScript Frameworks Addy Osmani Eng manager, Web DevRel Abhinav Rastogi Tech Lead, FlipkaD (Desktop)

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Frameworks can be fast if we put the work in.

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Fast is a product of using your framework well & intelligently loading via your bundler.

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4.2s Time-to-interactive

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4.8s Time-to-interactive

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bit.ly/ng2-weather Interactive in < 5s with AoT

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bit.ly/vue-hn Interactive in < 5s

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app coming soon Interactive in < 5s

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What do we mean by fast?

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Time-to-interactive <5s on a real-device over 3G *2s on repeat-load aVer Service Worker registered

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bit.ly/bundling-study

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What JS module bundler do you use? 83% webpack

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Do you use code-splitting to chunk up your JS? 58% yes JS JS JS 10%

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CONFIGURING WEBPACK

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tree-shaking 19% Service Worker 11% HTTP/2 14% What other concepts are you taking advantage of?

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POLYMER SHOP TIME TO INTERACTIVE NEXUS 5X - THROTTLED 3G NEXUS 5X - 3G W/PACKET LOSS 4.3s 5.8s

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FLIPKART NEXUS 5X - THROTTLED 3G NEXUS 5X - 3G W/PACKET LOSS 4.5s 6.9s HOUSING.COM TIME TO INTERACTIVE

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NEXUS 5X - THROTTLED 3G NEXUS 5X - 3G W/PACKET LOSS TIME TO INTERACTIVE (MEDIAN) 11s 12s * high of 24s. FVL in ~17s

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550ms script eval 270ms eval 524ms eval code for view 140ms eval cookie handling ~500KB script Interactive in 13 seconds ~3s, 249KB common vendor chunk ~5s load JS for view 8s parse/eval

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Try not to keep the main thread busy. Larger bundles impact interactivity & take longer to load, parse and execute.

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HTTPArchive average script size per page is 408KB gzipped 1MB script (250KB miniﬁed) JS Parse Time On Mobile

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Test on real phones & real networks. There’s no substitute.

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Less code, loaded becer improves ped. There is however, nuance.

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CODE-SPLITTING minimal functional code for a route

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System.import(‘./UserProfile’) .then(loadRoute(cb)) .catch(errorLoading); CODE-SPLITTING & ASYNC LOADING WEBPACK 1 WEBPACK 2 bit.ly/code-splicing-webpack2 bit.ly/code-splicing // Defines a “split-point” for a separate bundle require.ensure([], () => { const profile = require(‘./UserProfile’, cb); }); // Request when you require() const waitForChunk = require(‘bundle!./UserProfile.js’); waitForChunk(file => { // use file like is was require()'d }); BUNDLE-LOADER CALLS REQUIRE.ENSURE FOR YOU

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COMMON LIBRARY CHUNKS

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const CommonsChunkPlugin = require("webpack/lib/optimize/CommonsChunkPlugin"); module.exports = { entry: { p1: "./route-1", p2: "./route-2", p3: "./route-3" }, output: { filename: "[name].entry.chunk.js" }, plugins: [ new CommonsChunkPlugin("commons.chunk.js") ] } COMMON/VENDOR LIBRARY CHUNK SPLITTING

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THE PRPL PATTERN bit.ly/prpl-pacern

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require.ensure() async getComponent() React Router link rel=“preload” or HTTP/2 Push PRPL WITH WEBPACK bit.ly/prpl-webpack

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LINK REL=PRELOAD use with asset-webpack-plugin bit.ly/link-preload * For most apps using preload over H/2 Server Push will lead to better wins.

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module.exports = { entry: "./example", output: { path: path.join(__dirname, "js"), filename: "[chunkhash].js", chunkFilename: "[chunkhash].js" }, plugins: [ new webpack.optimize.AggressiveSplittingPlugin({ minSize: 30000, maxSize: 50000 }), // ... HTTP/2 with the AggressiveSplittingPlugin bit.ly/wepback-hcp2

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Code-splitting itself is not a panacea 9.8s TTI average

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#WhatsInYourBundle

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bit.ly/webpack-ped-preview

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3KB alternative to React with same ES6 API Interactive in <5s on real devices over 3G

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bit.ly/source-map-explorer Before (with React)

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bit.ly/source-map-explorer AVer (with Preact)

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bit.ly/source-map-explorer { resolve: { alias: { 'react': 'preact-compat', 'react-dom': 'preact-compat' } } } SETUP: USE THE PREACT-COMPAT ALIAS IN WEBPACK

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Layer your app so the network is an enhancement.

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INSTANT LOADING ON REPEAT. FASTER TTI FOR SUBSEQUENT VISITS.

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var CACHE_NAME = 'my-pwa-cache-v1'; var urlsToCache = [ '/', '/styles/styles.css', '/script/webpack-bundle.js' ]; self.addEventListener('install', function(event) { event.waitUntil( caches.open(CACHE_NAME) .then(function(cache) { // Open a cache and cache files return cache.addAll(urlsToCache); }) ); }); SERVICE WORKER

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APPLICATION SHELL ARCHITECTURE

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plugins: [ new SWPrecacheWebpackPlugin( { cacheId: "my-app", filename: "my-service-worker.js", staticFileGlobs: [ "app/css/**.css", "app/**.html", "app/js/**.js", "app/images/**.*" ], verbose: true } )] SW-PRECACHE WEBPACK PLUGIN bit.ly/wepback-precache

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HOUSING.COM FLIPKART Oline loading states

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SuppoD all target users using progressive enhancement.

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UNIVERSAL JS RENDERING & DATA-FLOW ReactDOMServer.renderToString() ComponentWillMount() Async data-flow with React Router React Resolver

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Universal JS has issues. Makes it easy to get stuck in uncanny valley renderToString() is synchronous so TTFB is long Streaming server rendered React can get a better TTBH. See react-dom-stream. renderToString() can monopolize the CPU, waste it re-rendering components for each page request. Bottleneck for pages w/lots of VDOM nodes Component memoization helps. See react-ssr-optimization.

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HIGH-PERFORMANCE REACT PWAs bit.ly/pwa-react

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Building Flipkart.com Abhinav Rastogi Tech Lead, Web Team @_abhinavrastogi

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Intro to Flipkart India’s largest e-commerce site and a ﬁrst-class PWA across all form factors and browsers!

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Mobile —> desktop

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React Flux/Redux React-Router Webpack Express Node Fetch Promises Babel Handlebars PM2 Karma

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Architecture Both mobile and desktop sites follow a similar architecture at the high level.

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Similarities • Route-based code splitting • Smart pre-loading of chunks and PRPL • Partial server-rendering • Service Workers

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Signiﬁcant differences: Mobile vs. Desktop Requirements User Behaviour Network Conditions Device Capabilities Browser Fragmentation

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Flipkart on Mobile • Build-time rendering • App shells • SW caches shell, ofﬂine-ﬁrst • Composition of multiple SPAs

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Flipkart on Desktop • Partial server-side rendering • No app shells • Chunked response for the ﬁrst request, allowing faster TTFP • SW used for caching data and resources

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What it looks like - Code Splitting

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What it looks like - PRPL

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Time to Interactive Search is available in the ﬁrst render and works without JS!

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Major Wins • Route-based code-splitting amortizes the high cost for the ﬁrst visit over the session • Smart preloading of chunks and PRPL makes the experience seam-less • Chunked-encoding allows us to download JS chunks while HTML is still being parsed • Based on UX requirement, solved repeat visits for mobile, ﬁrst visit for desktop

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Impact • Business: Upto 2x conversion during sale events • Business: Signiﬁcantly reduced bounce rate • SEO: 50% reduction in time taken by Google Search bots to crawl a page • SEO: 50% increase in number of pages indexed by Google Search • DevOps: Massive 70% reduction in desktop website tickets, lesser errors

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Gotchas • CORS in Webpack & route-based code-splitting • Cache-invalidation & the Webpack Manifest

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What’s Next

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Thank You! +Abhinav Rastogi @_abhinavrastogi @ﬂipkart_tech

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code.nasa.gov old Angular 1 site

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investigated ped issues

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bit.ly/nasa-ped-audit

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Best Practices Should Be Automated PRPL

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PRPL with code-splitting Lazy-loading fragments Ofﬂine Caching with Service Worker HTTP/2 + Server Push bundling Polymer App Toolbox

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Open Source Software Contributed by

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code.nasa.gov Implemented in <1 week 90+ score on Lighthouse Open Source and on GitHub now