Question

I have this function for returning the maximum value of an array:

Array.prototype.max = function() {

var max = this[0];
var len = this.length;

for (var i = 1; i < len; i++)
{

    if (this[i] > max)
    {       
        max = this[i];
    }
}

    return max;
}

When I use this array:

var data1Values = ['0','0','0','0','3','0','6','12']

data1Values.max() returns 6 instead of 12. It somehow skips the last value.

I’ve inserted alert(this[i]) and alert(max) inside the loop, and it recognizes both values (12 as this[i] and 6 as max) but it wont enter the condition.

What is happening here ?

Answer 1

You are comparing strings. “2” is greater than “1000”

Change to numbers or add parseInt(this[i],10)

DEMO

Array.prototype.max = function() {

  var len = this.length;
  var max = -1;
  for (var i=0; i < len; i++) {
    var val = parseInt(this[i],10);
    if (val > max) {       
        max = val;
    }
  }

  return max;
}

var data1Values = ['0','0','0','0','3','0','6','12']

alert(data1Values.max());