Function.createCallback

var createCallback = function(method, context) { return function() { //the arguements is passed in when the this callback //method is call //if there is parameter passed //package the parameter with the context //into an array, an invoke the callback //method with the array var l = arguments.length; if (l > 0) { var args = []; for (var i = 0; i < l; i++) { args[i] = arguments[i]; } //the last array member is the //the context args[l] = context; //apply with array argument return method.apply(this, args); } //if there is no parameters //just invoke the callback method with // the context as the only parameter return method.call(this, context); } } function eat(foodName, animalName) { alert(animalName + " eat " + foodName); } function Animal(name) { if (!name) { this.name = name; } else { this.name = "animal"; } //eat is the function will be called //name is the predetermined pass-in parameter //this parameter will be the last parameter in the function //the order paraemeter will be passed in when the callback is called this.eat = createCallback(eat, name); } var a = new Animal("fred"); //"grass" is passed in when callback is called a.eat("grass");