JS features you better know 1

In scope of functions arguments is local variable provides some nice features we can use in our code. First you don’t need to define any parameters for a function. You can just use arguments and will get arguments passed to the function.

    function sum(){
        var ret = 0;
        for (var i = 0; i < arguments.length; ++i) {
            ret += arguments[i];
        }
        return ret;
    }

    sum(1, 2, 3) //returns 6

Worth noting though that although we use arguments like an array, it’s not an actual javascript Array — it’s just an object. So you can’t do join(), pop(), push(), slice() and so forth.(You can convert it to a real array if you want: “var argArray = Array.prototype.slice.call(arguments);” )

arguments.callee property refers to the function that is currently running. It provides a way for unnamed function to refer to itself. This allows to make nice recursions:

    function fibonacci(){
        if (arguments.length == 1 && arguments[0] > 2) {
            return arguments.callee(arguments[0] - 2, [0, 1]);
        }
        if (arguments[0] == 0) {
            return arguments[1];
        }
        else {
            var len = arguments[1].length;
            return arguments.callee(arguments[0] - 1, arguments[1].concat(arguments[1][len - 1] + arguments[1][len - 2]));
        }
    }
    fibonacci(7) //returns [0, 1, 1, 2, 3, 5, 8]

Notice that “callee” property allows to do recursion with anonymous functions.

arguments.callee.caller property refers to a method called your function. This could be useful for example if you want to forbid public class creating and allow it for Factory only:

    function MyClass(){
        if (arguments.callee.caller != MyFactory.createObject) {
            throw new Error("There is no public constructor for MyClass.");
        }
        this.myproperty = "hello world";
    }