el-beeswarm
Version:
<div style="display: flex; padding: 1rem; flex-direction: column; align-items: center; justify-content: center; height: 100vh; text-align: center; display: flex;
23 lines (18 loc) • 471 B
JavaScript
;
/**
* If `map` already has the given `key`, returns its value. Otherwise, calls
* `callback`, adds the result to `map` at `key`, and then returns it.
*
* @template K
* @template V
* @param {Map<K, V>} map
* @param {K} key
* @param {() => V} callback
* @returns {V}
*/
module.exports = function (map, key, callback) {
if (map.has(key)) return /** @type {V} */ (map.get(key));
const value = callback();
map.set(key, value);
return value;
};