es-toolkit/dist/array/flatten.mjs

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

function flatten(arr, depth = 1) {
    const result = [];
    const flooredDepth = Math.floor(depth);
    const recursive = (arr, currentDepth) => {
        for (let i = 0; i < arr.length; i++) {
            const item = arr[i];
            if (Array.isArray(item) && currentDepth < flooredDepth) {
                recursive(item, currentDepth + 1);
            }
            else {
                result.push(item);
            }
        }
    };
    recursive(arr, 0);
    return result;
}

export { flatten };