locutus/ruby/Array/tally.js

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

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.tally = tally;
function tally(arr) {
    // parity verified: Ruby 3.3
    //      discuss at: https://locutus.io/ruby/Array/tally/
    //     original by: Kevin van Zonneveld (https://kvz.io)
    //          note 1: Counts occurrences by stringified key, mirroring `array.tally`.
    //       example 1: tally(['a', 'b', 'a'])
    //       returns 1: {a: 2, b: 1}
    //       example 2: tally([1, 2, 1, 3])
    //       returns 2: {'1': 2, '2': 1, '3': 1}
    //       example 3: tally([])
    //       returns 3: {}
    if (!Array.isArray(arr)) {
        return {};
    }
    const out = {};
    for (const value of arr) {
        const key = String(value);
        out[key] = (out[key] ?? 0) + 1;
    }
    return out;
}