Checking to see if a frame exists with jQuery

Question

I have found I can do the following: ``` if($('#notice', parent.frames['header'].document).length>0) { alert("It is here!"); } ``` to check for an item in another frame. Is there a way to find out of the frame exists? Specifically I am looking to see if parent.frames['header'].document is there. Is there a reliable way of doing this? Update: Here's my frameset code: ``` ``` I'm trying to make sure that I can access a div that lives inside of "header". The downside is that, in some cases, main is replaced with another frameset.

Accepted Answer

If you want to know if an element exists, you have to check the length property, see the jQuery FAQ:

```
if ($('#myFrame').length) {
  alert('#myFrame exists');
}
```

In your case I think you want to :

```
if ($('frame[name=header]', parent).length) {
  alert('frame exists');
}
```

Why check the length property?

Because if you pass a selector to jQuery that doesn't match anything, the returned result is a jQuery object, is not a falsy value (null, undefined, 0 or false), in an if statement the condition is evaluated to bool, and a non 'falsy' value is evaluated always to true:

```
if ($('#nonExisting')) {
  alert('always true');
}

// because 
!!$('#nonExisting') == true;  // and
!!'hello' == true;
!!0 == false;
```

I used `!!` as an example of a simple way of turning any expression into its boolean equivalent, what the if statement does behind the scenes...

Edit: Looking at your frameset markup, and assuming that you want to check if the header frame exists from the main page, you can easily do it by :

```
 if (parent.header !== undefined) {
   // frame exists
 }
```

Or simply:

```
 if (parent.header) {
   // frame exists
 }
```

Check this example:

- Frameset Page

- Main Page

Checking to see if a frame exists with jQuery

Solution

Problem