How to access a method/field of a constructor from a nested function

Question

I'm trying to access a field of a constructor from a nested function.

Here is my code:

var Box = function() {
  this.div = $("div#mydiv");
  this.guide = {
     div: $("div#mydiv2"),
     scroll: function() {
        $(document).scrollTo(this.div); //Want to scroll to mydiv2
        alert(Box.div.attr("id")); //Want to alert mydiv id
                                   //How do I access the div field of the Box constructor?
     }
  }
}

if I call the scroll method like this:

var a = new Box();

$("#button").click(function() {
a.guide.scroll();
});

Box.div is returning as undefined.

If I try to alert the id of the div property inside the scroll method as this.div it will use the div property inside the guide object. I've tried referencing the div field outside the guide object by using Box.div but this does not work. Please help me figure this out.

Rene Pot · Accepted Answer · 2012-04-02 22:06:19Z

2

Add this to the first row of the Box function:

var Box = function() {
    var self = this;

Then in the alert, use self instead of this as this is not referring to the top level function (box).

$(document).scrollTo(self.div);

edited Apr 2, 2012 at 22:06

answered Apr 2, 2012 at 21:55

Rene Pot

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3 Comments

dopatraman Over a year ago

@Topener--so does self always refer to the top level function?

Rene Pot Over a year ago

@codeninja yes, because you defined self there, it does refer to that this

dopatraman Over a year ago

@Topener--Thank you. The answer seems obvious after you learn it haha!

Tuan · Accepted Answer · 2012-04-02 22:02:51Z

2

It's because the "this" objects in your scroll function refers to the function itself. You need to cache a reference to the outermost "this" object and use it instead. See this fiddle for an example:

http://jsfiddle.net/tuando/kBc5K/

answered Apr 2, 2012 at 22:02

Tuan

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