text: 'use strict';
  
  if (!Array.prototype.indexOf) {
    Array.prototype.indexOf = function (what, start) {
      if (this === undefined || this === null) {
        throw new TypeError();
      }
      var length = this.length;
      start = +start || 0;
      if (Math.abs(start) === Infinity) {
        start = 0;
      } else if (start < 0) {
        start += length;
        if (start < 0) { start = 0; }
      }
      for (; start < length; start++) {
        if (this[start] === what) {
          return start;
        }
      }
      return -1;
    };
  }
  