Question

I have a javascript class that looks like this:

function xyPoint(x, y)
{
    this. x = x;
    this.y = y;

    this.hasX = function()
    {
        return (this.x != null);
    }

    this.dumbFunction = function()
    {
        if (this.hasX())
            //do something
    }
}

How do I get this this.hasX() to execute? It does not seem to work.

Answer 1

Using that pattern will eat memory like candy, you are creating a new closure every time you instantiate xyPoint.. Don’t define any functions inside the constructor. Use the prototype object so they are only defined once:

function xyPoint(x, y)
{
    this. x = x;
    this.y = y;

}

xyPoint.prototype = {

    constructor: xyPoint,

    hasX: function(){
    return (this.x != null);
    },

    dumbFunction: function(){

        if (this.hasX())
        //do something

    }

};

Now that the important thing has been said… you would use it like this (both versions):

var a = new xyPoint( 1,2 );
a.hasX() //true