function CommaFormatted(amount) {
     var delimiter = ","; // replace comma if desired
     var a = amount.split('.',2)
     var d = a[1];
     var i = parseInt(a[0]);
     if(isNaN(i)) { return ''; }
     var minus = '';
     if(i < 0) { minus = '-'; }
     i = Math.abs(i);
     var n = new String(i);
     var a = [];
     while(n.length > 3) {
          var nn = n.substr(n.length-3);
          a.unshift(nn);
          n = n.substr(0,n.length-3);
     }
     if(n.length > 0) { a.unshift(n); }
     n = a.join(delimiter);
     if(d.length < 1) { amount = n; }
     else { amount = n + '.' + d; }
     amount = minus + amount;
     return amount;
}

This function assumes what is being submitted to it is a string, with a decimal point and two places after the decimal. To get your number into that format first, use this.

Then this function will properly comma separate the number. For example, 2345643.00 will return 2,345,643.00

Put Comma Values in Numbers

JavaScript