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node_modules/mem/index.js 1.04 KB
aaac7fed   liuqimichale   add
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  'use strict';
  const mimicFn = require('mimic-fn');
  
  const cacheStore = new WeakMap();
  
  const defaultCacheKey = function (x) {
  	if (arguments.length === 1 && (x === null || x === undefined || (typeof x !== 'function' && typeof x !== 'object'))) {
  		return x;
  	}
  
  	return JSON.stringify(arguments);
  };
  
  module.exports = (fn, opts) => {
  	opts = Object.assign({
  		cacheKey: defaultCacheKey,
  		cache: new Map()
  	}, opts);
  
  	const memoized = function () {
  		const cache = cacheStore.get(memoized);
  		const key = opts.cacheKey.apply(null, arguments);
  
  		if (cache.has(key)) {
  			const c = cache.get(key);
  
  			if (typeof opts.maxAge !== 'number' || Date.now() < c.maxAge) {
  				return c.data;
  			}
  		}
  
  		const ret = fn.apply(null, arguments);
  
  		cache.set(key, {
  			data: ret,
  			maxAge: Date.now() + (opts.maxAge || 0)
  		});
  
  		return ret;
  	};
  
  	mimicFn(memoized, fn);
  
  	cacheStore.set(memoized, opts.cache);
  
  	return memoized;
  };
  
  module.exports.clear = fn => {
  	const cache = cacheStore.get(fn);
  
  	if (cache && typeof cache.clear === 'function') {
  		cache.clear();
  	}
  };