code: function indexOf(array, value) {
    if (Array.prototype.indexOf) {
      return array.indexOf(value, Number(arguments[2]) || 0);
    }
    var len = array.length >>> 0, from = Number(arguments[2]) || 0;
    from = (from < 0) ? Math.ceil(from) : Math.floor(from);
  
    if (from < 0) from += len;
  
    for (; from < len; from++) {
      if (from in array && array[from] === value) return from;
    }
    return -1;
  }
docs: IE8-safe wrapper for `Array.prototype.indexOf()`.
  
  @param {Array} array A JavaScript array.
  @param {*} value A value to search the array for.
  @return {Number} Returns the array index value of `value`, or `-1` if not present.