I accidentally came across `$(undefined)` in a statement below, where `params` is an object:

```
var $this = $(params._this) || $(this);

```

This did not work, as `$(params._this)` is a jQuery object and is always evaluated to `true`.

Funny enough, I was not sure how to check for it. It is not an empty object (i.e. `$.isEmptyObject($(undefined)) == false`), nor is it a function or a "plain object" (i.e. `$.isPlainObject()`).

I ended up modifying the statement to the following:

```
var $this = (params._this == undefined) ? $(params._this) : $(this);

```

My question is, is there any way to "evaluate" (not sure what word to use) `$(undefined)`? Is there any use for this?