Regex for positive lookahead thousand separator that would not mach numbers after dot

Question

I am using following regex to \'insert\' commas into numbers in javascript.

(\\d)(?=(\\d{3})+(?!\\d))

It works very well with integers however

Answer 1

You can achieve this only in 3 steps:

1. Split the number into integer and decimal parts
2. Modify the integer part
3. Join.

There is no variable-width look-behind in JS that would be very handy here.

var s = ".12345680000454554";
//Beforehand, perhaps, it is a good idea to check if the number has a decimal part
if (s.indexOf(".") > -1) { 
    var splts = s.split(".");
    //alert(splts);
    splts[0] = splts[0].replace(/(\d)(?=(\d{3})+(?!\d))/g, '$1,');
    //alert(splts[0]);
    s = splts.join(".");
    alert(s);
  }
else
  {
     alert(s.replace(/(\d)(?=(\d{3})+(?!\d))/g, '$1,'));
  }