JavaScript – Add Commas To Numbers

At times, I have had to add commas to numbers in order to make them look better in different applications. Even though there isn’t a native way to do this in JavaScript, the code can be quite short, sweet and to the point:

function addCommas(intNum) {
  return (intNum + '').replace(/(\d)(?=(\d{3})+$)/g, '$1,');

The downside of the above function is that it will only work for integers. Here is a function that will get the job done for one number or a string which contains one or more numbers:

function delimitNumbers(str) {
  return (str + "").replace(/\b(\d+)((\.\d+)*)\b/g, function(a, b, c) {
    return (b.charAt(0) > 0 && !(c || ".").lastIndexOf(".") ? b.replace(/(\d)(?=(\d{3})+$)/g, "$1,") : b) + c;

First this function forces the parameter that was passed in to become a string. Next, a global replace of a regular expression looking for a four-digit or longer number goes through and inserts the commas in the correct place. After that, the result is returned as a string.

Here are some tests that I ran on the function to make sure that it works correctly:

// Delimit a random number.
alert("Random number:  " + delimitNumbers(Math.random() * (1 << 30)));

// Delimit all powers of 2 (from 2^0 to 2^30) in a string.
var powersOf2 = Array.range(31).map(function(i){return 1 << i});
alert("Powers of 2:\n" + delimitNumbers(powersOf2.join("\n")));

One thing you want to keep in mind if you choose to test the delimitNumbers() function with the above code is the fact that you will need to make sure that Array.range() and are correctly defined. I did my test in the ScriptBox which always uses the newest version of jPaq (currently an alpha of v2.0).

Escape & Unescape – Deprecated?

Two of the most widely used JavaScript functions that are now deprecated are the escape() and unescape() functions. This means that in order to ensure that your code will continue to work in all future browsers, you should use one of the alternative functions as was indicated on MDN:

  • encodeURI()
  • decodeURI()
  • encodeURIComponent()
  • decodeURIComponent()

What To Do When They Are No More

Since these functions may not always exist, I decided to write the necessary JavaScript code to make sure they can continue to be used:

(function() {
var objGlobal = this;
if(!(objGlobal.escape && objGlobal.unescape)) {
  var escapeHash = {
    _ : function(input) {
      var ret = escapeHash[input];
      if(!ret) {
        if(input.length - 1) {
          ret = String.fromCharCode(input.substring(input.length - 3 ? 2 : 1));
        else {
          var code = input.charCodeAt(0);
          ret = code < 256
            ? "%" + (0 + code.toString(16)).slice(-2).toUpperCase()
            : "%u" + ("000" + code.toString(16)).slice(-4).toUpperCase();
        escapeHash[ret] = input;
        escapeHash[input] = ret;
      return ret;
  objGlobal.escape = objGlobal.escape || function(str) {
    return str.replace(/[^\w @\*\-\+\.\/]/g, function(aChar) {
      return escapeHash._(aChar);
  objGlobal.unescape = objGlobal.unescape || function(str) {
    return str.replace(/%(u[\da-f]{4}|[\da-f]{2})/gi, function(seq) {
      return escapeHash._(seq);


I created these functions based on information found at


I personally love both JavaScript and Python. For this reason, from time to time I like to port functions that are available in Python, over to JavaScript. The following is a port of the expandTabs function.

String.prototype.expandTabs = function(tabSize) {
  tabSize = Math.min(Math.max(parseInt(+tabSize || 8), 1), 32);
  return this.replace(/^.*\t.*$/gm, function(line) {
    var allBefore = "";
    return line.replace(/(.*?)(\t+)/g, function(match, before, tabs) {
      allBefore += before;
      tabs = new Array(1 + tabSize * tabs.length - allBefore.length % tabSize).join(" ");
      allBefore += tabs;
      return before + tabs;

The biggest difference between this JavaScript version and the Python version is the limitation of a 32 character tab size. If you want to increase the maximum tab size, simply change 32 to something else.