Largest & Second Largest Algos

gistfile1.txt

    Array.prototype.largest_number =function() {
      var largest;
      for (var i=0; i<this.length; i++) {
        var num = this[i];
        if(largest === undefined){
          largest = num;
        } else if (num > largest) {
            largest = num;
        }
      }
      return largest;
    }

    Array.prototype.second_largest_number =function() {
      var largest = this.largest_number(),
          secondLargest;
      for (var i=0; i<this.length; i++) {
        var num = this[i];
        if(secondLargest === undefined){
          secondLargest = num;
        } else if (num > secondLargest && num < largest) {
          secondLargest = num;
        }
      }
      return secondLargest;
    }

    console.log('largest number is: ', [1,5,9,2,22,89,24,11,4,9].largest_number());
    console.log('second largest number is ', [1,5,9,2,22,89,24,11,4,9].second_largest_number());