Deep Flatten

deepFlatten.js

/**
 * A utility function to flatten an array, nested to any depth.
 * @param {Array} initialArray
 *
 */
function deepFlatten(initialArray) {
    return initialArray.reduce((acc, v) => {
        return acc.concat(Array.isArray(v) ? deepFlatten(v) : v);
    }, []);
}


/**
 * Example usage
 */

// Example array
const test = [[1, 2, [3]], 4];

console.log(deepFlatten(test));
// [1,2,3,4]