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March 29, 2018 02:21
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Memoize an async function by storing its results
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| function defaultHasher() { | |
| return JSON.stringify(arguments); | |
| } | |
| function asyncMemoize(fn, hasher=defaultHasher) { | |
| async function memozie() { | |
| let cache = memozie.cache; | |
| const key = hasher(arguments); | |
| if (!cache.hasOwnProperty(key)) { | |
| cache[key] = await fn.apply(this, arguments); | |
| } | |
| return cache[key]; | |
| } | |
| memozie.cache = {}; | |
| return memozie; | |
| } |
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| // test | |
| function fetch(data) { | |
| return new Promise((resolve) => { | |
| setTimeout(function () { | |
| resolve(data) | |
| }, 1000) | |
| }) | |
| } | |
| const fetchMemoize = asyncMemoize(fetch); | |
| const now = Date.now(); | |
| fetchMemoize('user').then(function() { | |
| console.log(`fetch user cost time ${Date.now() - now}`); | |
| let current = Date.now(); | |
| fetchMemoize('user').then(function() { | |
| console.log(`fetch user cost time ${Date.now() - current}`); | |
| }) | |
| }) | |
| fetchMemoize('role').then(function() { | |
| console.log(`fetch role cost time ${Date.now() - now}`); | |
| }) |
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