call() and apply()

obj.method.call(another_obj, param1, param2)
obj.method.apply(another_obj, [param1, param2])

function f() {
   var args = [].slice.call(arguments, 1, 3);
   return args;
}

>>> f(1, 2, 3, 4, 5, 6)
2,3

[].slice.call can also be Array.prototype.slice.call

function one() {
    alert(1);
    return function() {
        alert(2);
    }
}
>>> my = one(); // alerts 1
>>> my(); // alerts 2

Adding properties to the function objects, e.g. cache, 'coz functions are objects

function myFunc(param){
    if (!myFunc.cache) {
        myFunc.cache = {};
    }
    if (!myFunc.cache[param]) {
        var result = {}; // …
        myFunc.cache[param] = result;
    }
    return myFunc.cache[param];
}

a is private, sayAh() is privileged

function MyConstr() {
    var a = 1;
    this.sayAh = function() {
        return a;
    };
}

>>> new MyConstr().sayAh();