insert sort implementation

insert-sort.js

var array = [1,7,5,9,0,4,12,56,7,0,45,8,2,3,6,7,8,1,5,0];
Array.prototype.move = function (old_index, new_index) {
    if (new_index >= this.length) {
        var k = new_index - this.length;
        while ((k--) + 1) {
            this.push(undefined);
        }
    }
    this.splice(new_index, 0, this.splice(old_index, 1)[0]);
    return this; // for testing purposes
};
var insertion_sort = function (unsorted) {
  for(var i=1;i<unsorted.length;i++) {
    var current = unsorted[i];
    var j = i - 1;
    while(j >= 0) {
      var compare = unsorted[j];
      if (current > compare) {
        break;
      }
      j--;
    }
    unsorted = unsorted.move(i, j+1);
  }
  return unsorted;
};

console.log(insertion_sort(array));