Add commas or spaces to group every three digits

Question

I have a function to add commas to numbers:

function commafy( num ) {
  num.toString().replace( /\\B(?=(?:\\d{3})+)$/g, \",\" );
}

Unfortun

Answer 1

I have extended #RobG's answer a bit more and made a sample jsfiddle

function formatNum(n, prec, currSign) {
    if(prec==null) prec=2;
  var n = ('' + parseFloat(n).toFixed(prec).toString()).split('.');
  var num = n[0];
  var dec = n[1];
  var r, s, t;

  if (num.length > 3) {
    s = num.length % 3;

    if (s) {
      t = num.substring(0,s);
      num = t + num.substring(s).replace(/(\d{3})/g, ",$1");
    } else {
      num = num.substring(s).replace(/(\d{3})/g, ",$1").substring(1);
    }
  }
    return (currSign == null ? "": currSign +" ") + num + (dec? '.' + dec : '');
}
alert(formatNum(123545.3434));
alert(formatNum(123545.3434,2));
alert(formatNum(123545.3434,2,'€'));

and extended same way the #Ghostoy's answer

function commafy( num, prec, currSign ) {
    if(prec==null) prec=2;
    var str = parseFloat(num).toFixed(prec).toString().split('.');
    if (str[0].length >= 5) {
        str[0] = str[0].replace(/(\d)(?=(\d{3})+$)/g, '$1,');
    }
    if (str[1] && str[1].length >= 5) {
        str[1] = str[1].replace(/(\d{3})/g, '$1 ');
    }
    return (currSign == null ? "": currSign +" ") + str.join('.');
}

alert(commafy(123545.3434));