Equivalent of String.format in jQuery

Equivalent of String.format in jQuery

I’m trying to move some JavaScript code from MicrosoftAjax to JQuery. I use the JavaScript equivalents in MicrosoftAjax of the popular .net methods, e.g. String.format(), String.startsWith(), etc. Are there equivalents to them in jQuery?


Solution 1:

The source code for ASP.NET AJAX is available for your reference, so you can pick through it and include the parts you want to continue using into a separate JS file. Or, you can port them to jQuery.

Here is the format function…

String.format = function() {
  var s = arguments[0];
  for (var i = 0; i < arguments.length - 1; i++) {       
    var reg = new RegExp("\\{" + i + "\\}", "gm");             
    s = s.replace(reg, arguments[i + 1]);

  return s;

And here are the endsWith and startsWith prototype functions…

String.prototype.endsWith = function (suffix) {
  return (this.substr(this.length - suffix.length) === suffix);

String.prototype.startsWith = function(prefix) {
  return (this.substr(0, prefix.length) === prefix);

Solution 2:

This is a faster/simpler (and prototypical) variation of the function that Josh posted:

String.prototype.format = String.prototype.f = function() {
    var s = this,
        i = arguments.length;

    while (i--) {
        s = s.replace(new RegExp('\\{' + i + '\\}', 'gm'), arguments[i]);
    return s;


'Added {0} by {1} to your collection'.f(title, artist)
'Your balance is {0} USD'.f(77.7) 

I use this so much that I aliased it to just f, but you can also use the more verbose format. e.g. 'Hello {0}!'.format(name)

Solution 3:

Many of the above functions (except Julian Jelfs’s) contain the following error:

js> '{0} {0} {1} {2}'.format(3.14, 'a{2}bc', 'foo');
3.14 3.14 afoobc foo

Or, for the variants that count backwards from the end of the argument list:

js> '{0} {0} {1} {2}'.format(3.14, 'a{0}bc', 'foo');
3.14 3.14 a3.14bc foo

Here’s a correct function. It’s a prototypal variant of Julian Jelfs’s code, which I made a bit tighter:

Related:  What are the benefits to using anonymous functions instead of named functions for callbacks and parameters in JavaScript event code?
String.prototype.format = function () {
  var args = arguments;
  return this.replace(/\{(\d+)\}/g, function (m, n) { return args[n]; });

And here is a slightly more advanced version of the same, which allows you to escape braces by doubling them:

String.prototype.format = function () {
  var args = arguments;
  return this.replace(/\{\{|\}\}|\{(\d+)\}/g, function (m, n) {
    if (m == "{{") { return "{"; }
    if (m == "}}") { return "}"; }
    return args[n];

This works correctly:

js> '{0} {{0}} {{{0}}} {1} {2}'.format(3.14, 'a{2}bc', 'foo');
3.14 {0} {3.14} a{2}bc foo

Here is another good implementation by Blair Mitchelmore, with a bunch of nice extra features: https://web.archive.org/web/20120315214858/http://blairmitchelmore.com/javascript/string.format

Solution 4:

Made a format function that takes either a collection or an array as arguments


format("i can speak {language} since i was {age}",{language:'javascript',age:10});

format("i can speak {0} since i was {1}",'javascript',10});


var format = function (str, col) {
    col = typeof col === 'object' ? col : Array.prototype.slice.call(arguments, 1);

    return str.replace(/\{\{|\}\}|\{(\w+)\}/g, function (m, n) {
        if (m == "{{") { return "{"; }
        if (m == "}}") { return "}"; }
        return col[n];

Solution 5:

There is an (somewhat) official option: jQuery.validator.format.

Related:  jQuery + client-side template = “Syntax error, unrecognized expression”

Comes with jQuery Validation Plugin 1.6 (at least).
Quite similar to the String.Format found in .NET.

Edit Fixed broken link.

Solution 6:

If you’re using the validation plugin you can use:

jQuery.validator.format("{0} {1}", "cool", "formatting") = 'cool formatting'