Flatten Array - Javascript

flattenArray.js

function flattenArray(array) {
  var arrayPool = [];
  if(array.length > 0) {
    for(var i=0; i < array.length; i++){
      if(array[i].constructor === Array){
        arrayPool = arrayPool.concat(flattenArray(array[i]));
      } else {
        arrayPool.push(array[i]);
      }
    }
  }
  return arrayPool;
}

console.log(flattenArray([[1,2,[3]], 4]));