forked from daren.hsu/line_push
65 lines
1.4 KiB
JavaScript
65 lines
1.4 KiB
JavaScript
'use strict';
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const mimicFn = require('mimic-fn');
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const mapAgeCleaner = require('map-age-cleaner');
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const cacheStore = new WeakMap();
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const mem = (fn, options = {}) => {
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// Automatically use WeakMap unless the user provided their own cache
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const weakCache = options.cache || new WeakMap();
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const {
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cacheKey = ([firstArgument]) => firstArgument,
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cache = new Map(),
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maxAge
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} = options;
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if (typeof maxAge === 'number') {
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mapAgeCleaner(cache);
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}
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const memoized = function (...arguments_) {
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const key = cacheKey(arguments_);
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// Prefer WeakMap if the key allows it
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const bestCache = key && (typeof key === 'object' || typeof key === 'function') ?
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weakCache :
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cache;
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if (bestCache.has(key)) {
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return bestCache.get(key).data;
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}
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const cacheItem = fn.apply(this, arguments_);
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bestCache.set(key, {
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data: cacheItem,
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maxAge: maxAge ? Date.now() + maxAge : Infinity
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});
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return cacheItem;
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};
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try {
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// The below call will throw in some host environments
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// See https://github.com/sindresorhus/mimic-fn/issues/10
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mimicFn(memoized, fn);
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} catch (_) {}
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cacheStore.set(memoized, cache);
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return memoized;
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};
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module.exports = mem;
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module.exports.clear = fn => {
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if (!cacheStore.has(fn)) {
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throw new Error('Can\'t clear a function that was not memoized!');
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}
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const cache = cacheStore.get(fn);
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if (typeof cache.clear === 'function') {
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cache.clear();
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}
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};
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