Add commas to a numeric value

[mburt]

Hi,
I'm wondering how you would add commas to a number, say, in an <input> tag.
Ex.
1
12
123
1,234
12,345
123,456
1,234,567

I really want to know how to do this! I've seen similar scripts, but it is very confusing. Thank-you.

[Twey]

Number.prototype.withThousandsSeparator = function(sep) {
  var s = this.toString(),
    y = (s.indexOf(".") > -1 ? s.substring(s.indexOf(".")) : "");
  if(y) s = s.substring(0, s.indexOf("."));
  for(var i = s.length - 3;i > 0;i -= 3) {
    var front = s.substring(0, i),
      back = s.substring(i);
    s = front + sep + back;
  }
  return s + y;
}

[mburt]

How do I access this function?

[Twey]

var num = 1234567;
window.alert(num.withThousandsSeparator(','));

[mburt]

Wow you're good