Knockout startbinding.

starbinding.js

ko.bindingHandlers.starRating = {
    init: function(element, valueAccessor) {
        $(element).addClass("starRating");
        for (var i = 0; i < 5; i++)
           $("<span>").appendTo(element);
           
            // Handle mouse events on the stars
            $("span", element).each(function(index) {
                $(this).hover(
                    function() { $(this).prevAll().add(this).addClass("hoverChosen") }, 
                    function() { $(this).prevAll().add(this).removeClass("hoverChosen") }                
                ).click(function() { 
                   var observable = valueAccessor();  // Get the associated observable
                   observable(index+1);               // Write the new rating to it
                 });
            });
    },
    update: function(element, valueAccessor) {
        // Give the first x stars the "chosen" class, where x <= rating
        var observable = valueAccessor();
        $("span", element).each(function(index) {
            $(this).toggleClass("chosen", index < observable());
        });
    }
};