locutus/esm/ruby/Array/flatten.js

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

export function flatten(arr, depth) {
    // parity verified: Ruby 3.3
    //      discuss at: https://locutus.io/ruby/Array/flatten/
    //     original by: Kevin van Zonneveld (https://kvz.io)
    //          note 1: Returns a new array that is a one-dimensional flattening of the array.
    //       example 1: flatten([1, [2, 3, [4, 5]]])
    //       returns 1: [1, 2, 3, 4, 5]
    //       example 2: flatten([1, [2, [3, [4]]]], 1)
    //       returns 2: [1, 2, [3, [4]]]
    //       example 3: flatten([[1, 2], [3, 4]])
    //       returns 3: [1, 2, 3, 4]
    if (!Array.isArray(arr)) {
        return [];
    }
    if (depth === undefined) {
        depth = Infinity;
    }
    return arr.flat(depth);
}