Forked from paulirish/performance.now()-polyfill.js
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August 29, 2015 14:08
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// relies on Date.now() which has been supported everywhere modern for years. | |
// as Safari 6 doesn't have support for NavigationTiming, we use a Date.now() timestamp for relative values | |
// if you want values similar to what you'd get with real perf.now, place this towards the head of the page | |
// but in reality, you're just getting the delta between now() calls, so it's not terribly important where it's placed | |
(function(){ | |
// prepare base perf object | |
if (typeof window.performance === 'undefined') { | |
window.performance = {}; | |
} | |
if (!window.performance.now){ | |
var nowOffset = Date.now(); | |
if (performance.timing && performance.timing.navigationStart){ | |
nowOffset = performance.timing.navigationStart | |
} | |
window.performance.now = function now(){ | |
return Date.now() - nowOffset; | |
} | |
} | |
})(); |
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