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August 27, 2022 15:55
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Layout thrashing browser optimization demo
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| <!doctype html> | |
| <html lang="en"> | |
| <head> | |
| <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta/css/bootstrap.min.css" | |
| integrity="sha384-/Y6pD6FV/Vv2HJnA6t+vslU6fwYXjCFtcEpHbNJ0lyAFsXTsjBbfaDjzALeQsN6M" crossorigin="anonymous"> | |
| <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css" | |
| integrity="sha384-HSMxcRTRxnN+Bdg0JdbxYKrThecOKuH5zCYotlSAcp1+c8xmyTe9GYg1l9a69psu" crossorigin="anonymous"> | |
| <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap-theme.min.css" | |
| integrity="sha384-6pzBo3FDv/PJ8r2KRkGHifhEocL+1X2rVCTTkUfGk7/0pbek5mMa1upzvWbrUbOZ" crossorigin="anonymous"> | |
| <link href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css" rel="stylesheet" | |
| integrity="sha384-EVSTQN3/azprG1Anm3QDgpJLIm9Nao0Yz1ztcQTwFspd3yD65VohhpuuCOmLASjC" crossorigin="anonymous"> | |
| <style id="theStyle"> | |
| /* the goal of these selectors is to be stupidly unperformant */ | |
| body:nth-child(2):not(.unused) div:nth-child(2) *[even="true"]:nth-child(even) + *[odd="true"]:nth-child(odd) { | |
| font-size: 1.2em; | |
| } | |
| body:nth-child(2):not(.unused) div:nth-child(2) * :nth-child(even) { | |
| background: aqua; | |
| } | |
| body:nth-child(2):not(.unused) div:nth-child(2) * :nth-child(odd) { | |
| background: chocolate; | |
| } | |
| body:nth-child(2):not(.unused) div:nth-child(2) * :nth-child(even) + :nth-child(odd) { | |
| font-weight: bold; | |
| } | |
| body:nth-child(2):not(.unused) div:nth-child(2) * :nth-child(odd) + :nth-child(even) { | |
| font-size: 1.1em; | |
| } | |
| body:nth-child(2):not(.unused) div:nth-child(2) * [even="true"]:nth-child(even) + [odd="true"]:nth-child(odd) { | |
| font-weight: bold; | |
| } | |
| body:nth-child(2):not(.unused) div:nth-child(2) *:nth-child(even) { | |
| height: 40px; | |
| overflow: hidden; | |
| } | |
| body:nth-child(2):not(.unused) div:nth-child(2) *:nth-child(odd) { | |
| height: 30px; | |
| overflow: hidden; | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <template id="theHtml"> | |
| <div> | |
| <div class="row align-items-start" even="false"> | |
| <div class="col" even="false"> | |
| One of three columns | |
| </div> | |
| <div class="col" even="true"> | |
| One of three columns | |
| </div> | |
| <div class="col" even="false"> | |
| One of three columns | |
| </div> | |
| </div> | |
| <div class="row align-items-center" even="true"> | |
| <div class="col" even="false"> | |
| One of three columns | |
| </div> | |
| <div class="col" even="true"> | |
| One of three columns | |
| </div> | |
| <div class="col" even="false"> | |
| One of three columns | |
| </div> | |
| </div> | |
| <div class="row align-items-end" even="false"> | |
| <div class="col" even="false"> | |
| One of three columns | |
| </div> | |
| <div class="col" even="true"> | |
| One of three columns | |
| </div> | |
| <div class="col" even="false"> | |
| One of three columns | |
| </div> | |
| </div> | |
| </div> | |
| </template> | |
| <div> | |
| <button type="button" id="doThrash" style="all: revert">Thrash?</button> | |
| <pre id="display"></pre> | |
| </div> | |
| <div id="container"> | |
| </div> | |
| <script type="module"> | |
| for (let i = 0; i < 10; i++) { | |
| container.appendChild(theHtml.content.cloneNode(true)) | |
| } | |
| for (let i = 0; i < 100; i++) { | |
| const clone = theStyle.cloneNode(true) | |
| clone.id = '' | |
| document.head.appendChild(clone) | |
| } | |
| const doIt = () => { | |
| const channel = new MessageChannel(); | |
| channel.port1.onmessage = () => { | |
| performance.mark('end') | |
| performance.measure('total', 'start', 'end') | |
| display.innerHTML += performance.getEntriesByType('measure').slice(-1)[0].duration + '\n' | |
| } | |
| requestAnimationFrame(() => { | |
| performance.mark('start') | |
| function thrash() { | |
| const el = document.querySelector('.col') | |
| performance.mark('loop') | |
| for (let i = 0; i < 1000; i++) { | |
| el.style.width = '1px' | |
| el.getBoundingClientRect() | |
| } | |
| performance.measure('loop', 'loop') | |
| } | |
| thrash() | |
| channel.port2.postMessage(undefined) | |
| }) | |
| } | |
| doThrash.addEventListener('click', () => doIt(true)) | |
| </script> | |
| </body> | |
| </html> |
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