locutus/esm/ruby/Array/filter_map.js

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

export function filter_map(values, callback) {
    //      discuss at: https://locutus.io/ruby/Array/filter_map/
    // parity verified: Ruby 3.3
    //     original by: Kevin van Zonneveld (https://kvz.io)
    //          note 1: Maps each value and keeps only callback results that are neither false nor nil.
    //       example 1: filter_map([1, 2, 3, 4], (value) => (value % 2 === 0 ? value : null))
    //       returns 1: [2, 4]
    //       example 2: filter_map(['a', 'bb', 'ccc'], (value) => (value.length > 1 ? value + value : null))
    //       returns 2: ['bbbb', 'cccccc']
    //       example 3: filter_map([], (value) => value)
    //       returns 3: []
    if (typeof callback !== 'function') {
        throw new TypeError('filter_map(): callback must be a function');
    }
    if (!Array.isArray(values)) {
        return [];
    }
    const out = [];
    for (let index = 0; index < values.length; index += 1) {
        const value = values[index];
        const mapped = callback(value, index, values);
        if (mapped !== false && mapped !== null && mapped !== undefined) {
            out.push(mapped);
        }
    }
    return out;
}