es-toolkit/dist/map/reduce.mjs

A state-of-the-art, high-performance JavaScript utility library with a small bundle size and strong type annotations.

function reduce(map, callback, initialValue) {
    if (initialValue == null && map.size === 0) {
        throw new TypeError('Reduce of empty map with no initial value');
    }
    let accumulator = initialValue;
    for (const [key, value] of map) {
        if (accumulator == null) {
            accumulator = value;
        }
        else {
            accumulator = callback(accumulator, value, key, map);
        }
    }
    return accumulator;
}

export { reduce };