text: var BigInt = this.BigInt || function () {
      var map = {};
  
      function BigInt(a) {
          if (this instanceof BigInt) {
              if (map[a]) return map[a];
              this.val = a;
              map[a] = this;
          }
          else if (a instanceof BigInt) return a;
          else return new BigInt(a);
      };
      var prototype = new BigInt;
      prototype.toString = function () {
          return this.val;
      };
      prototype.valueOf = function () {
          return this;
      }
      BigInt.prototype = prototype;
      return BigInt;
  }()     
  