jsApplyExample.js

function foo(){
    var callback = arguments[0] || function(){return "do nothing"};
    var options = arguments[1] || {};
    return [callback(), options.a || "no A", options.b || "no B", this];
}

// try these out to understand how to use apply and what it means to write functions which might be called in this way
foo(null, {a:1, b:2});
foo.apply("apples", [function(){return "do something"}, {a:1, b:2}]);