Flatten array JS

flattenArray.js

var flattenArray = function(arr) {
  var results = [];
  arr.forEach(function(item) {
    if(Array.isArray(item)) {
      results = results.concat(flattenArray(item));
    } else {
      results.push(item);
    }
  });
  return results;
}

var myArr = [2, [ 3, 4, [ 5 ] ,[ 6, [ 7, [ 8 ]]], 5]];

console.log(flattenArray(myArr));