Help with JS and functions parameters

Question

Does JS support two functions with the same name and different parameters ?

function f1(a, b)
{
// a and b are numbers
}

function f1(a, b, c)
{
// a is a string         


        

Answer 1

You can also use instanceof, example with basic polymorphism.

First create a superclass (ball)

// superclass
function Ball() {
    this.play = function() {
        alert("Ball throw");
    };
}

and now for some subclasses (types of balls)

// subclass
function Basketball() {
    this.play = function() {
        alert("basketball throw");
    };
}
// subclass
function Soccerball() {
    this.play = function() {
        alert("soccer ball kick/throw");
        console.debug("here");
    };
}
// subclass
function Baseball() {
    this.play = function() {
        alert("strike 3 you're out");
        console.debug("here");
    };
}

Give them Ball functionality, aka set their superclass via prototype

// set subclass functionality
Basketball.prototype = new Ball();
Soccerball.prototype = new Ball();
Baseball.prototype = new Ball();

Some polymorphism (create a bunch of balls and play with them all, but play based on type)

var bunchOfBalls = [new Baseball(), new Soccerball(), new Basketball()];
for (var i = 0; i < bunchOfBalls.length; i++) {
    bunchOfBalls[i].play();
}

Now write a function that takes a ball but only want to to work for specific type of balls (mimic function overloading, more or less)

//overloading dependent upon type
function BasketbalOrBaseballOnlyPlay(aBall) {
    if (aBall instanceof Basketball) {
        //special basketball function
    }
    if (aBall instanceof Baseball) {
        //special baseball function
    }

}

If aBall is a Basketball so aBall = new Basketball(); then aBall instanceof Basketball would return true for Basketball and false for baseball but true for Ball.

So aBall instanceof Ball would return true because a Basketball is a Ball.

See code live at http://jsfiddle.net/kLCPB/