Jquery, What does slice return on failure?

Question

I can't find this anywhere, how do you check to see if slice is returning elements still in the list? Like $('.class').slice(n-th,n-th);

When n-th variables are increased throughout the index of the return class by slicing, how do you know when slice returns on an invalid index? Hope I explained that well.

Here is the example code of what I'm trying to accomplish:

$(window).scroll(function() {
    if(!($('embed').slice(p1,p2).show())){
        $(window).unbind('scroll');
    }
    ++p1;++p2;
}

Also, why is my event not unbinding?

Thanks for any assistance :)

Answer 1

Simply test slice().length to see if you got anything back, or you can test it for a specific length.

In your case:

var $mySlice = $('embed').slice(p1,p2); // <== Store slice

  // Check that slice returned 1+ elements
if( $mySlice.length ) { 

      // show them if yes
    $mySlice.show();
} else {

      // unbind if no
    $(window).unbind('scroll');
}

In general you want to look at:

$( ... ).slice( ... ).length

The above simply tests for 1+ elements. If you're slicing off N elements and you want to make sure that you get a full and complete result, simply modify to

if ( $mySlice.length == N ) {

---

jQuery's .slice() never returns things beyond the end of the remaining elements. It's smart enough to know when to stop.

If you give it an end point that exceeds the number of elements, it'll return the elements that exist, then it'll stop without a runtime error.

Answer 2

Slice just returns an empty array if you pass it bad arguments.