Javascript custom callback

refer to http://stackoverflow.com/questions/2190850/javascript-create-custom-callback

functionThing(name){
    this.name = name;
}
Thing.prototype.doSomething =function(callback, salutation){
    // Call our callback, but using our own instance as the context
    callback.call(this, salutation);
}

function foo(salutation){
    alert(salutation +" "+this.name);
}

var t =newThing('Joe');
t.doSomething(foo,'Hi');  // Alerts "Hi Joe" via `foo`