Question

I was reading an article here:

http://javascriptweblog.wordpress.com/2010/03/16/five-ways-to-create-objects/

It tells about five ways of creating objects. But my question is one of his way (3) is:

myApp.Notepad = function(defaultFont) {
    var  that = {};
    that.writeable = true;
    that.font = defaultFont;
    that.setFont = function(theFont) {
        that.font = theFont;
    }
    return that;
}

myApp.notepad1 =  myApp.Notepad('helvetica');

As per author, we can use it when multiple instances are needed we can use any pattern from 3 (above) to 5.

But as far as I know, we do need to use this keyword which reflects back newly created instances and refers to only that instance. However above, author uses that object instead of this and also there is no new keyword used above. How will it apply to multiple object instances ? Is it essentially same as using this?

Answer 1

In your example, that is a new object created by this line:

var that = {};

The function then proceeds to set the properties of this object.

On the other hand, this is used with a constructor function — when called using new, a new object is automatically created and passed to the function as this. The same example could be written as:

myApp.Notepad = function(defaultFont) {
    this.writeable = true;
    this.font = defaultFont;
    this.setFont = function(theFont) {
        this.font = theFont;
    }
}

myApp.notepad1 = new myApp.Notepad('helvetica');