map-fns/modifyInMap/index.js

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

'use strict';

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var __assign = function() {
    __assign = Object.assign || function __assign(t) {
        for (var s, i = 1, n = arguments.length; i < n; i++) {
            s = arguments[i];
            for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p)) t[p] = s[p];
        }
        return t;
    };
    return __assign.apply(this, arguments);
};

/**
 * Creates a new `map` populated with every key in the original `map` where the
 * value behind each `k` in `keys` is the return value of `fn(map[k])`
 *
 * ```tsx
 * const out = modifyInMap({ a: 1, b: 2 }, "b", n => n + 1);
 * console.log(out); // { a: 1, b: 3 }
 * ```
 *
 * The original `map` is not modified.
 *
 * An error is thrown if any key in `keys` does not exist in the map.
 *
 * @param map - The map to copy and modify.
 * @param keys - The keys to modify within the map.
 * @returns A new map with modified values.
 */
function modifyInMap(map, keys, fn) {
    var obj = __assign({}, map);
    var keyList = (Array.isArray(keys) ? keys : [keys]);
    for (var _i = 0, keyList_1 = keyList; _i < keyList_1.length; _i++) {
        var key = keyList_1[_i];
        if (!obj.hasOwnProperty(key)) {
            throw new Error("Key '".concat(key, "' does not exist in map."));
        }
        obj[key] = fn(obj[key]);
    }
    return obj;
}

module.exports = modifyInMap;