webpack/lib/util/memoize.js

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
*/

"use strict";

/** @template T @typedef {function(): T} FunctionReturning */

/**
 * @template T
 * @param {FunctionReturning<T>} fn memorized function
 * @returns {FunctionReturning<T>} new function
 */
const memoize = fn => {
	let cache = false;
	/** @type {T | undefined} */
	let result = undefined;
	return () => {
		if (cache) {
			return /** @type {T} */ (result);
		} else {
			result = fn();
			cache = true;
			// Allow to clean up memory for fn
			// and all dependent resources
			// eslint-disable-next-line no-warning-comments
			// @ts-ignore
			fn = undefined;
			return /** @type {T} */ (result);
		}
	};
};

module.exports = memoize;