Add asset hitrate

[omrilotan]

• Bug fix
• New feature
• Breaking change
• Deprecations
• Tests added
• Doc added

cachehit

Get resource browser cache cachehit (0 - 1 number)

import { cachehit } from 'page-timing';

const rate = await cachehit(); // 0.855

Pass in a filter function to get results for a subset of resources:

// Javascript files only
const javascriptCacheHitRate = await cachehit({
    filter: ({ name }) => /.m?js[$\?]/.test(name),
    limit: 50
});

// Specific domain
const myCDNCacheHitRate = await cachehit({
    filter: ({ name }) => /https:\/\/[\w-]*.mycdn.com/.test(),
    limit: 50
});

Arguments

• filter: A filter function to create a subset of files we want to get cache rate for. This function accepts one argument: a PerformanceResourceTiming object. The default is no filter (all resources).
• limit: A number, in milliseconds, which represents resource load duration that we consider served from cache. The default is 50.

† There are two types of browser cache: memory cache and disk cache. Memory cache will have a duration of 0 (limit: 0) and disk cache will have a higher duration, while still relatively low. For this reason, the default limit value is 50 (milliseconds). This gives a close estimation of browser cache hit-rate.