text: /**
   * 实现 strStr()
   *
   * @param {string} haystack
   * @param {string} needle
   * @return {number}
   */
  var strStr = function (haystack, needle) {
    return haystack.indexOf(needle);
  };
  
  var haystack = 'aaaaa',
    needle = ' ';
  
  var result = strStr(haystack, needle);
  console.log(result);
  