map-fns/mapPartialMap/index.js

<h1 align="center"> <code>map-fns</code> </h1>

'use strict';

/**
 * Creates a new map populated with every key in `keys` where the value
 * behind each `k` in `keys` is `callback(map[k])`.
 *
 * ```tsx
 * mapPartialMap({ a: 1, b: 2, c: 3 }, ["a", "c"], (n) => n * 2);
 * //=> {
 * //     a: 2,
 * //     c: 6,
 * //   }
 * ```
 *
 * @param map The original map.
 * @param keys The keys to include in the new map.
 * @param callback A function that takes a single argument `map[k]` and returns the value of `newMap[k]`.
 * @returns A new `map` where `map[k]` is the result of `callback(map[k])`.
 */
function mapPartialMap(map, keys, callback) {
    var obj = {};
    for (var _i = 0, keys_1 = keys; _i < keys_1.length; _i++) {
        var key = keys_1[_i];
        if (!map.hasOwnProperty(key)) {
            throw new Error("Key '".concat(key, "' does not exist in map."));
        }
        obj[key] = callback(map[key]);
    }
    return obj;
}

module.exports = mapPartialMap;