mathjs
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Math.js is an extensive math library for JavaScript and Node.js. It features a flexible expression parser with support for symbolic computation, comes with a large set of built-in functions and constants, and offers an integrated solution to work with dif
23 lines (20 loc) • 472 B
JavaScript
/*
MIT License http://www.opensource.org/licenses/mit-license.php
Author Tobias Koppers @sokra
*/
;
/**
* @template K
* @template V
* @param {Map<K, V>} map a map
* @param {K} key the key
* @param {function(): V} computer compute value
* @returns {V} value
*/
exports.provide = (map, key, computer) => {
const value = map.get(key);
if (value !== undefined) return value;
const newValue = computer();
map.set(key, newValue);
return newValue;
};