Used to display formatted money via Knockout binding

ko-money.js

(function(){

	var toMoney = function(num){
		return '$' + (num.toFixed(2).replace(/(\d)(?=(\d{3})+\.)/g, '$1,') );
	};

	var handler = function(element, valueAccessor, allBindings){
		var $el = $(element);
		var method;

		// Gives us the real value if it is a computed observable or not
		var valueUnwrapped = ko.unwrap( valueAccessor() );

		if($el.is(':input')){
			method = 'val';
		} else {
			method = 'text';
		}
		return $el[method]( toMoney( valueUnwrapped ) );
	};

	ko.bindingHandlers.money = {
		update: handler
	};
})();

test.html

<span data-bind="money: 1234567.2"></span> <!-- Outputs $1,234,567.20 -->

<input type="text" data-bind="money: 1234567"> <!-- Sets value to $1,234,567.00 -->

Another option for the toMoney function, just as an illustration for the curious (in coffeescript):

toMoney = (value) ->
  options =
    currency: 'CAD'
    style: 'currency'
    maximumFractionDigits: 2
  return value.toLocaleString(locale, options)

Cheers