“кэширование в JavaScript” Ответ

кэширование в JavaScript

// to create a cache, you can use an IIFE to return a function with access to a local variable:
const functionWithCache = (function() {
	const cache = {};
	return function(num) {
		// example: returns whether an input number is even or not
		return num % 2 === 0;
	};
})();

// you can use this to memoize functions:
const memoizedFunction1 = (function() {
	const cache = {};
	return function(num) {
		if (num in cache) {
			return cache[num];
		}
		// example: returns whether an input number is even or not
		return cache[num] = num % 2 === 0;
	};
})();

// for more complex parameters:
const memoizedFunction2 = (function() {
	const cache = {};
	return function() {
		const cacheQuery = Array.from(arguments).map((arg) => JSON.stringify(arg)).join(",");
		if (cacheQuery in cache) {
			return cache[cacheQuery];
		}
		// function body
		return cache[cacheQuery] = result;
	};
})();

// with that we can create a function to convert other functions into memoized functions:
function memoize(func) {
	const cache = {};
	return function() {
		const args = Array.from(arguments);
		const cacheQuery = args.map((arg) => JSON.stringify(arg)).join(",");
		if (cacheQuery in cache) {
			return cache[cacheQuery];
		}
		return cache[cacheQuery] = func(...args);
	};
}