code: function indexOf(list, item) {
    if (NATIVE_ARRAY_INDEXOF) {
      return NATIVE_ARRAY_INDEXOF.call(list, item);
    }
  
    for (var i = 0; i < list.length; i++) {
      if (list[i] === item) {
        return i;
      }
    }
  
    return -1;
  }
docs: Backwards compatible Array.prototype.indexOf
  @param {array} list List of items.
  @param {object} item Item to search for.
  @return {number} Index of match or -1 if not found.