fcc_steamroller.js

// freecodecamp
// intermediate algorith scripting
// steamroller

function steamrollArray(arr) {
  // create array to push non array items in to
  var arr2 = [];

  // create function that will flatten arrays
  function flat(curr) {
    // check if item being passed is an array
    if (!Array.isArray(curr)) {
      // if not -> push in to arr2
      arr2.push(curr);
    // if item passed in to flat function is an array
    } else {
      // loop through each item of the array
      curr.forEach(function(c) {
        flat(c); // recursive call to flatten array
      });
    }
  }
  // call flat function in each arr initally passed through streamrollArray function
  arr.forEach(flat);
  // return flattened array
  return arr2;
}

// tests
console.log(steamrollArray([1, [2], [3, [[4]]]])); // returns [1, 2, 3, 4]
console.log(steamrollArray([[["a"]], [["b"]]])); // returns ["a", "b"]
console.log(steamrollArray([1, {}, [3, [[4]]]])); // returns [1, {}, 3, 4]