locutus/ruby/Array/group_by.js

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

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.group_by = group_by;
function group_by(arr) {
    // parity verified: Ruby 3.3
    //      discuss at: https://locutus.io/ruby/Array/group_by/
    //     original by: Kevin van Zonneveld (https://kvz.io)
    //          note 1: Groups array elements by identity key, mirroring `array.group_by { |v| v }`.
    //       example 1: group_by(['a', 'b', 'a'])
    //       returns 1: {a: ['a', 'a'], b: ['b']}
    //       example 2: group_by([1, 2, 1, 3])
    //       returns 2: {'1': [1, 1], '2': [2], '3': [3]}
    //       example 3: group_by([])
    //       returns 3: {}
    if (!Array.isArray(arr)) {
        return {};
    }
    const out = {};
    for (const value of arr) {
        const key = String(value);
        const existing = out[key];
        if (existing) {
            existing.push(value);
        }
        else {
            out[key] = [value];
        }
    }
    return out;
}