The Hitchhiker's Guide to the Front-End Performance, 2019 edition

This year's edition of: https://speakerdeck.com/ythecombinator/the-hitchhikers-guide-to-the-front-end-performance-2018-edition

1. The Hitchhiker's Guide to the Front-End Performance The Hitchhiker's Guide to the Front-End Performance 2019 EDITION
2. ˜ I’m from… ˜
6. !!!
7. What do we know about perf? What do we know about perf?
8. ˜ GZIP everything ˜ Minify both CSS and JS ˜ HTML must be compressed ˜ CSS goes on <head> ˜ JS goes lastly on </body> ˜ Optimize all the images (e.g. svgo)
9. Issues I was facing Issues I was facing
10. ˜ What I do at …
11. ˜ JavaScript ˜
12. "Write modern, idiomatic JavaScript, and let the JavaScript engine worry about making it fast." - Mathias Bynens, BrazilJS 2018
13. ˜ JavaScript ˜
14. Before version 5.9 of V8 came out, the engine used two compilers: ˜ Full Codegen A simple and very fast compiler that produced simple and relatively slow machine code ˜ Crankshaft A more complex (Just-In-Time) optimizing compiler that produced highly-optimized code
15. Optimization Killers
16. Optimization Killers ~ Generators and async functions ~ for-of and destructuring ~ try-catch and try-finally ~ Compound let or const assignment ~ Object literals that contain __proto__, or get or set declarations. ~ debugger or with statements ~ Literal calls to eval() ~ …
17. Performance cliffs in Crankshaft (function good() {
 const start = Date.now();
 for (var i = 0; i < 1e8; i++) {}
 console.log(Date.now() - start);
 })(); ˜80ms (function bad() {
 const start = Date.now();
 for (var i = 0; i < 1e8; i++) {}
 console.log(Date.now() - start);
 const whatever = 1;
 })(); ˜230ms
18. Performance cliffs in Crankshaft (function good() {
 const start = Date.now();
 for (var i = 0; i < 1e8; i++) {}
 console.log(Date.now() - start);
 })(); (function bad() {
 const start = Date.now();
 for (var i = 0; i < 1e8; i++) {}
 console.log(Date.now() - start);
 const whatever = 1;
 })(); ˜3x slowdown with Crankshaft
20. The new execution pipeline is built on top of Ignition, V8’s interpreter, and TurboFan, V8’s newest optimizing compiler.
21. Optimization Killers ~ Generators and async functions ~ for-of and destructuring ~ try-catch and try-finally ~ Compound let or const assignment ~ Object literals that contain __proto__, or get or set declarations. ~ debugger or with statements ~ Literal calls to eval() ~ …
22. 60% faster web developer tools http://v8project.blogspot.com/2017/11/web-tooling-benchmark.html
23. https://twitter.com/popeindustries/status/895575424406867968
24. "Write modern, idiomatic JavaScript, and let the JavaScript engine worry about making it fast." - Mathias Bynens, BrazilJS 2018
27. ˜ fixing perf issues be like ˜
28. ˜ fixing perf issues be like ˜
29. ˜ Problems ˜
30. ˜ #1 ˜ Critical Resources Late Delivered
31. ˜ Connecting to critical origins (preconnect) ˜ Asset for current page (preload) ˜ Asset for future navigation (prefetch)
32. ˜ Connecting to critical origins (preconnect) ˜ Asset for current page (preload) ˜ Asset for future navigation (prefetch)
33. <link rel="preconnect" href="https://fonts.googleapis.com/" crossorigin> <link rel="preconnect" href="https://fonts.gstatic.com/" crossorigin> ˜ What says… ˜ What can $% do…
34. ˜ What it does… Preconnect allows the browser to setup early connections before an HTTP request is actually sent to the server. This includes: ˜ DNS lookups ˜ TLS negotiations ˜ TCP handshakes This in turn: ✔ Eliminates roundtrip latency ✔ Saves time for users
35. ˜ Bring me the ! 100MS 200MS 300MS 400MS 500MS 600MS 700MS HTML CSS FONT 1 FONT 2 Fonts start loading Fonts rendered
36. ˜ Bring me the ! 100MS 200MS 300MS 400MS 500MS 600MS 700MS HTML CSS FONT 1 FONT 2 Fonts start loading Fonts rendered FONT 1 FONT 2
37. ˜ Connecting to critical origins (preconnect) ˜ Asset for current page (preload) ˜ Asset for future navigation (prefetch)
38. <link rel="preload" href="https://example.com/fonts/font.woff" as="font" crossorigin> ˜ What says… ˜ What can $% do…
39. ˜ What it does… Some of the benefits of the preload directive include: ✔ Gives the browser the ability to determine the resource type (it can tell if the same resource can be reused in the future) ✔ The browser can determine if the request is compliant with the content security policy ✔ The browser can send the appropriate accept headers based on resource type
40. ˜ Connecting to critical origins (preconnect) ˜ Asset for current page (preload) ˜ Asset for future navigation (prefetch)
41. ˜ What it does… ✔ Fetch resources in the background (idle time) ✔ Store them in the browser’s cache It can be:
42. Link Prefetching DNS Prefetching Prerendering
43. Link Prefetching DNS Prefetching Prerendering ˜ What it does… Allows the browser to fetch resources, store them in cache, assuming that the user will request them. <link rel="prefetch" href="/uploads/images/pic.png"> ˜ What can $% do…
44. Link Prefetching DNS Prefetching Prerendering ˜ What it does… Allows the browser to perform DNS lookups on a page in the background while the user is browsing. <link rel=“dns-prefetch” href="#$fonts.googleapis.com"> ˜ What can $% do…
45. Link Prefetching DNS Prefetching Prerendering ˜ What it does… Allows the browser to render the entire page in the background, all the assets of a document. <link rel=“prerender” href=“https://xandaviao.com.br/”> ˜ What can $% do…
46. Link Prefetching DNS Prefetching Prerendering ˜ What it does… Allows the browser to render the entire page in the background, all the assets of a document. <link rel=“prerender” href=“https://xandaviao.com.br/”> ˜ What can $% do… ⚠ ❌ ❌ ⚠
47. Link Prefetching DNS Prefetching Prerendering ˜ What it does… Allows the browser to render the entire page in the background, all the assets of a document. <link rel=“prerender” href=“https://xandaviao.com.br/”> ˜ What can $% do… ✘ You want to be more careful with prerendering as it is resource heavy and can cause bandwidth waste, especially on mobile devices
48. https://wicg.github.io/priority-hints/
49. %%%& A script is to be loaded with critical importance as it is necessary for the core user experience ''( <script src=foo importance=critical> %%%& An image is to be loaded with high importance. It could be important but not critical to the overall experience loading up. ''( <img src=foo importance=high> %%%& It can be used to indicate low importance/non-blocking style which isn't impacting the core experience. ''( <link rel=stylesheet href=foo importance=low>
50. #$ First import(/* webpackPrefetch: 3 */ "assets/images/foo.jpg"); #$ Second import(/* webpackPrefetch: 2 */ "modules/foo"); #$ Last import(/* webpackPrefetch: 1 */ “modules/bar");
51. Preloaded Chunk Prefetched Chunk X
52. Preloaded Chunk Prefetched Chunk X ˜ Starts loading in parallel to the parent chunk ˜ Focuses on current navigation ˜ Fetches resources with high-priority ˜ Is instantly downloaded ˜ Starts after the parent chunk finish ˜ Focuses on fetching resources for the next navigation ˜ Fetches resources with low priority ˜ Is downloaded in browser idle time
53. ˜ Connecting to critical origins (preconnect) ˜ Asset for current page (preload) ˜ Asset for future navigation (prefetch)
54. ˜ #2 ˜ Blocked First Paint
55. ˜ Avoid invisible text while web fonts are loading ˜ Reduce render blocking scripts and stylesheets ˜ Server-side render stuff
56. ˜ Avoid invisible text while web fonts are loading ˜ Reduce render blocking scripts and stylesheets ˜ Server-side render stuff
57. ˜ What says… ˜ What can $% do… @font-face { font-family: "Open Sans Regular"; src: url(“./OpenSans-Regular-BasicLatin.woff2") format("woff2"); font-display: swap; }
58. ˜ What says… ˜ What can $% do… @font-face { font-family: "Open Sans Regular"; src: url(“./OpenSans-Regular-BasicLatin.woff2") format("woff2"); font-display: swap; } ˜ What it does… The initial font displayed is the first system font in the stack. When the custom font has loaded, it will kick in and replace the system font that was initially displayed.
59. ˜ Avoid invisible text while web fonts are loading ˜ Reduce render blocking scripts and stylesheets ˜ Server-side render stuff
60. ˜ What says… ˜ What can $% do… https://github.com/addyosmani/critical
61. ˜ Avoid invisible text while web fonts are loading ˜ Reduce render blocking scripts and stylesheets ˜ Server-side render stuff
62. https://rauchg.com/2014/7-principles-of-rich-web-applications
63. https://nextjs.org
64. ˜ Avoid invisible text while web fonts are loading ˜ Reduce render blocking scripts and stylesheets ˜ Server-side render stuff
65. ˜ #3 ˜ Bloated Pages
66. ˜ Audit your assets regularly ˜ Code Split (Routes, Components, Vendor bundles) + Dynamic Import stuff ˜ Remove unused library code + Tree Shake
67. ˜ Audit your assets regularly ˜ Code Split (Routes, Components, Vendor bundles) + Dynamic Import stuff ˜ Remove unused library code + Tree Shake
68. Bundlephobia Import Cost for VSCode Webpack Bundle Analyzer
69. ˜ Audit your assets regularly ˜ Code Split (Routes, Components, Vendor bundles) + Dynamic Import stuff ˜ Remove unused library code + Tree Shake
70. 1.8s bootup 0.78s bootup ˜ What says… ˜ What can $% do…
71. 1.8s bootup 0.78s bootup ˜ What says… ˜ What can $% do… 56% faster
72. ˜ Audit your assets regularly ˜ Code Split (Routes, Components, Vendor bundles) + Dynamic Import stuff ˜ Remove unused library code + Tree Shake
73. https://github.com/GoogleChromeLabs/webpack-libs-optimizations
76. ˜ Audit your assets regularly ˜ Code Split (Routes, Components, Vendor bundles) + Dynamic Import stuff ˜ Remove unused library code + Tree Shake
77. ˜ #4 ˜ Unnecessary Resources
78. ˜ Compress (gzip, brotli)
79. ˜ -30%
82. ⚠ ❌ ❌ ⚠
83. ˜ Compress (gzip, brotli)
84. ˜ #5 ˜ Unused Code
85. ˜ Code coverage in DevTools (Page load, runtime) ˜ Lighthouse Coverage Audit ˜ Remove unused code to improve load time ˜ Write regression tests
86. ˜ Code coverage in DevTools (Page load, runtime) ˜ Lighthouse Coverage Audit ˜ Remove unused code to improve load time ˜ Write regression tests
87. 95% unused
88. ˜ Code coverage in DevTools (Page load, runtime) ˜ Lighthouse Coverage Audit ˜ Remove unused code to improve load time ˜ Write regression tests
89. https://github.com/purifycss/purifycss
90. ˜ Code coverage in DevTools (Page load, runtime) ˜ Lighthouse Coverage Audit ˜ Remove unused code to improve load time ˜ Write regression tests
91. (+ jest-image-snapshot)
92. ˜ Code coverage in DevTools (Page load, runtime) ˜ Lighthouse Coverage Audit ˜ Remove unused code to improve load time ˜ Write regression tests
93. ˜ #6 ˜ Unoptimized Images
94. ˜ Optimize images ˜ Use lighter formats ˜ Use responsive images
95. ˜ Optimize images ˜ Use lighter formats ˜ Use responsive images
96. ˜ What says…
97. ˜ GUI ˜ ImageOptmin (Mac) XNConvert (Cross-platform) ˜ Build ˜ imagemin libvips ˜ CDN ˜ Cloudinary Imgix Fastly Akamai ˜ CDN ˜ (self-hosted) Thumbor ImageFlow ˜ What can $% do…
98. ˜ GUI ˜ ImageOptmin (Mac) XNConvert (Cross-platform) ˜ Build ˜ imagemin libvips ˜ CDN ˜ Cloudinary Imgix Fastly Akamai ˜ CDN ˜ (self-hosted) Thumbor ImageFlow
99. ˜ What it does…
100. ˜ Optimize images ˜ Use lighter formats ˜ Use responsive images
101. <img src="banda_magnificos.gif"> 7.3mb <video autoplay muted playinline> <source src="banda_magnificos.mp4" type="video/mp4"> </video> 1.3MB <video autoplay muted playinline> <source src=“banda_magnificos.webm” type=“video/webm"> </video> 960kb 80%+ savings
102. ˜ Optimize images ˜ Use lighter formats ˜ Use responsive images
103. https://developer.mozilla.org/en-US/docs/Web/API/NetworkInformation/effectiveType
104. https://developer.mozilla.org/en-US/docs/Web/API/NetworkInformation/effectiveType
105. https://developer.mozilla.org/en-US/docs/Web/API/NetworkInformation/effectiveType
107. 4G+ (Video) ˜1mb 2G-3G (Static Image) ˜30kb
108. ˜ Optimize images ˜ Use lighter formats ˜ Use responsive images
109. ˜ #7 ˜ Wasted Renders
111. Virtualizing a list of items involves maintaining a window and moving that window around your list. "How does windowing work?" by Brian Vaughn
112. https://github.com/bvaughn/react-virtualized
113. 10K items wo/ virtualization 10K items w/ virtualization X
114. w/ virtualization X wo/ virtualization "Rendering large lists with react-window" by Addy Osmani
115. w/ virtualization X wo/ virtualization "Rendering large lists with react-window" by Addy Osmani
116. w/ virtualization X wo/ virtualization ˜242.7ms ˜2.4ms "Rendering large lists with react-window" by Addy Osmani
117. ˜ Use referentially equal stuff ˜ Use PureComponent/memo (when it makes sense) ˜ (In the future) Take benefit from time slicing ˜ Take benefit from techniques like windowing
118. "In God we trust; all others must bring data." - W. Edwards Deming
119. ˜ Senior Software Engineer, Front- End @beakyn ˜ @ythecombinator on the webs ˜ addicted to emojis, memes and beer
120. https://speakerdeck.com/ ythecombinator/the-hitchhiker-s-guide-to-the-front-end-performance-2019-edition
122. Thanks Thanks