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The Art of Lazy Loading
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Houssein Djirdeh
October 03, 2018
Technology
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490
The Art of Lazy Loading
The magic of lazy loading images and splitting bundles ✨
Houssein Djirdeh
October 03, 2018
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Transcript
the art of lazy loading lazy loading @hdjirdeh
lazy defer until the user needs it
loading fetch + render
what?
images!
None
highest high medium low low high highest medium low
highest high medium low low high highest medium low
low highest high medium low low high highest medium
highest high medium low low high highest medium medium low
> 40% of data fetched = images
scroll event listeners
<img class="lazy" data-src="kittens.png"> class="lazy" data-src="kittens.png"
let image = document.querySelector("img.lazy"); const lazyLoad = () "=> {
setTimeout(() "=> { if ( image.getBoundingClientRect().top "<= window.innerHeight "&& image.getBoundingClientRect().bottom ">= 0 ) { image.src = image.dataset.src; } }, 200); }; document.addEventListener("scroll", lazyLoad); let image = document.querySelector("img.lazy"); const lazyLoad = () "=> { setTimeout(() "=> { if ( image.getBoundingClientRect().top "<= window.innerHeight "&& image.getBoundingClientRect().bottom ">= 0 ) { image.src = image.dataset.src; } }, 200); } document.addEventListener("scroll", lazyLoad); };
intersection observer
let image = document.querySelector("img.lazy"); let lazyObserver = new IntersectionObserver(entry "=>
{ if (entry.isIntersecting) { const image = entry.target; image.src = lazyImage.dataset.src; lazyObserver.unobserve(image); } }); lazyObserver.observe(image); let image = document.querySelector("img.lazy"); let lazyObserver = new IntersectionObserver(entry "=> { if (entry.isIntersecting) { const image = entry.target; image.src = lazyImage.dataset.src; lazyObserver.unobserve(image); } }); lazyObserver.observe(image);
bit.ly/inter-obs
native browser feature?
<img lazyload=“on”> lazyload=“on”
None
what else?
code!
None
1 KB of Image 1 KB of JavaScript ≠
split, split, split ✂
import('lodash.sortby') .then(module "=> module.default) .then(doSomethingCool) import('lodash.sortby') .then(module "=> module.default) .then(doSomethingCool)
dynamic import
what should I do?
audit
None
None
None
audit fix ✂
None
Use a library lozad.js lazysizes yall.js
Use IO + polyfill Use a library Use placeholders/ load
early
Use placeholders/ load early pinterest pinterest.com
Use placeholders/ load early lqip-loader github.com/zouhir/lqip-loader
Use placeholders/ load early Primitive primitive.lol
Use placeholders/ load early sqip github.com/technopagan/sqip SQIP LQIP Image
None
export const routes: Routes = [ { path: 'main', component:
'MainComponent', }, { path: 'details', loadChildren: 'details/details.module#DetailsModule' } ]; angular router
const DetailsComponent = () "=> import(‘./details.vue'); export const router =
new VueRouter({ routes: [ { path: '/details', component: DetailsComponent }, ] }) const DetailsComponent = () "=> import(‘./details.vue'); export const router = new VueRouter({ routes: [ { path: '/details', component: DetailsComponent }, ] }) const DetailsComponent = () "=> import(‘./details.vue'); export const router = new VueRouter({ routes: [ { path: '/details', component: DetailsComponent }, ] }) export const router = new VueRouter({ routes: [ { path: '/details', component: DetailsComponent }, ] }) vue router
import { Router } from 'preact-router'; import Home from '"../routes/home';
import Details from 'async!./details'; export const App = () "=> ( <Router> <Home path="/" "/> <Details path="/details/" "/> "</Router> ); import { Router } from 'preact-router'; import Home from '"../routes/home'; import Details from 'async!./details'; export const App = () "=> ( <Router> <Home path="/" "/> <Details path="/details/" "/> "</Router> ); preact cli import { Router } from 'preact-router'; import Home from '"../routes/home'; import Details from 'async!./details'; export const App = () "=> ( <Router> <Home path="/" "/> <Details path="/details/" "/> "</Router> );
const loadPage = (page) "=> (dispatch) "=> { switch(page) {
case 'view1': import('"../my-view1.js').then((module) "=> { "// ""... }); break; "//""... } dispatch(updatePage(page)); }; const loadPage = (page) "=> (dispatch) "=> { switch(page) { case 'view1': import('"../my-view1.js').then((module) "=> { "// ""... }); break; "//""... } dispatch(updatePage(page)); }; const loadPage = (page) "=> (dispatch) "=> { switch(page) { case 'view1': import('"../my-view1.js').then((module) "=> { "// ""... }); break; "//""... } dispatch(updatePage(page)); }; polymer pwa-starter-kit
import Loadable from 'react-loadable'; const DetailsComponent = Loadable({ loader: ()
"=> import('./details.component'), loading: () "=> <div>Loading""..."</div>, }); import Loadable from 'react-loadable'; const DetailsComponent = Loadable({ loader: () "=> import('./details.component'), loading: () "=> <div>Loading""..."</div>, }); import Loadable from 'react-loadable'; const DetailsComponent = Loadable({ loader: () "=> import('./details.component'), loading: () "=> <div>Loading""..."</div>, }); jamiebuilds / react-loadable
import loadable from 'loadable-components'; const DetailsComponent = loadable(() "=> import('./details.component'),
{ LoadingComponent: () "=> <div>Loading""..."</div> }); import loadable from 'loadable-components'; const DetailsComponent = loadable(() "=> import('./details.component'), { LoadingComponent: () "=> <div>Loading""..."</div> }); import loadable from 'loadable-components'; const DetailsComponent = loadable(() "=> import('./details.component'), { LoadingComponent: () "=> <div>Loading""..."</div> }); smooth-code / loadable-components
import LoadableVisibility from ‘react-loadable-visibility/react-loadable' const DetailsComponent = LoadableVisibility({ loader: ()
"=> import('./details.component'), loading: () "=> <div>Loading""..."</div>, }) import LoadableVisibility from ‘react-loadable-visibility/react-loadable' const DetailsComponent = LoadableVisibility({ loader: () "=> import('./details.component'), loading: () "=> <div>Loading""..."</div>, }) import LoadableVisibility from ‘react-loadable-visibility/react-loadable' const DetailsComponent = LoadableVisibility({ loader: () "=> import('./details.component'), loading: () "=> <div>Loading""..."</div>, }) stratiformltd / react-loadable-visibility
None
const DetailsComponent = Loadable({ loader: () "=> import('./details.component'), loading: ()
"=> <div>Loading""..."</div>, delay: 300, }); jamiebuilds / react-loadable const DetailsComponent = Loadable({ loader: () "=> import('./details.component'), loading: () "=> <div>Loading""..."</div>, delay: 300, });
suspense
bit.ly/lazy-metro metro (react native)
None
audit fix ✂ observe
webpack-bundle-analyzer
size-plugin
progressivetooling.com
responsive images with srcset preload critical chunks convert gifs to
.mp4 pre-cache assets using a service worker compress assets remove unused packages module / nomodule
/ Dx Ux
@hdjirdeh