What is the purpose of a 'name :' label ?

[vmars316]

Hello & Thanks ,

I am making my way thru game tutorial -

http://www.w3schools.com/games/tryit.asp?filename=trygame_controllers_keys

and I would like to know , what is the purpose of a 'name :' label ( canvas : , start : , clear : ) ?

var myGameArea = {
    canvas : document.createElement("canvas"),
    start : function() {
        this.canvas.width = 480;
        this.canvas.height = 270;
        this.context = this.canvas.getContext("2d");
        document.body.insertBefore(this.canvas, document.body.childNodes[0]);
        this.interval = setInterval(updateGameArea, 20);
        window.addEventListener('keydown', function (e) {
            myGameArea.key = e.keyCode;
        })
        window.addEventListener('keyup', function (e) {
            myGameArea.key = false;
        })
    }, 
    clear : function(){
        this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
    }

Also , for ' ("canvas"), ' , why the comma ' , ' ?

 

Thanks

 

 

[davej]

See...

 

http://www.w3schools.com/js/js_objects.asp

[vmars316]

See...

 

http://www.w3schools.com/js/js_objects.asp

Ok , I see , those are just properties , just a more complex version of below:

var person = {
    firstName: "John",
    lastName : "Doe",
    id       :  5566
};

While I've got ya on the phone , let me ask :

window.addEventListener('keydown', function (e) {
            myGameArea.key = e.keyCode;
        }

is ' e ' a reserved word ?

Also

myGamePiece = new component(30, 30, "red", 10, 120);

is 'component' a reserved word ?

 

Pls , where can I find a list of all js reserved word ?

 

Thanks again..

 

[davej]

e is an event object which is passed by the function parameter list.

 

component is an object class which is apparently defined in the game. It isn't a reserved word in Javascript.

 

Reserved words...

 

http://www.w3schools.com/js/js_reserved.asp

[vmars316]

Thanks davej !