locutus/esm/ruby/Array/sample.js

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

export function sample(arr, n) {
    //  discuss at: https://locutus.io/ruby/Array/sample/
    // original by: Kevin van Zonneveld (https://kvz.io)
    //      note 1: Returns a random element, or n random elements, from the array.
    //      note 1: Uses Math.random() for randomness.
    //   example 1: [1, 2, 3].indexOf(sample([1, 2, 3])) !== -1
    //   returns 1: true
    //   example 2: sample([1, 2, 3], 2).length
    //   returns 2: 2
    if (!Array.isArray(arr) || arr.length === 0) {
        return n === undefined ? undefined : [];
    }
    if (n === undefined) {
        return arr[Math.floor(Math.random() * arr.length)];
    }
    // Fisher-Yates shuffle for selecting n unique elements
    const copy = arr.slice();
    const result = [];
    const count = Math.min(n, copy.length);
    for (let i = 0; i < count; i++) {
        const idx = Math.floor(Math.random() * copy.length);
        result.push(copy[idx]);
        copy.splice(idx, 1);
    }
    return result;
}