locutus/kotlin/collections/associateBy.js

Locutus other languages' standard libraries to JavaScript for fun and educational purposes

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.associateBy = associateBy;
function associateBy(values, keySelector) {
    //  discuss at: https://locutus.io/kotlin/collections/associateBy/
    // original by: Kevin van Zonneveld (https://kvz.io)
    //      note 1: Builds a key->element map using keySelector, with the last duplicate key winning (Kotlin associateBy behavior).
    //   example 1: associateBy(['ant', 'bear', 'cat'], (s) => s.charAt(0))
    //   returns 1: {a: 'ant', b: 'bear', c: 'cat'}
    //   example 2: associateBy([1, 2, 3, 4], (n) => n % 2)
    //   returns 2: {'0': 4, '1': 3}
    //   example 3: associateBy([], () => 'x')
    //   returns 3: {}
    if (!Array.isArray(values) || typeof keySelector !== 'function') {
        return {};
    }
    const out = {};
    for (let i = 0; i < values.length; i++) {
        const value = values[i];
        const key = String(keySelector(value, i, values));
        out[key] = value;
    }
    return out;
}