detecting the last list item in jquery/javascript

Question

I have a set of tab (main-tabs) on a website and each tab has another set of tabs (sub-tabs). I want to use arrow keys on a keyboard to navigate the tabs, instead of a mouse.

These tabs are just HTML list items <li>

When I reach the last sub-tab with the arrow key, I want it to go back to the next main tab so it can display its own sub-tabs, and carry on the navigation inside it.

My question is, how can I detect, in jQuery/javascript, when I've reached the last list item (tab) using the arrow keys i.e. the right arrow key?

Many Thanks

Answer 1

You might be able to use either the :last or :last-child selectors in jQuery. Depending on how your <li> tags are nested, you might also have to use the children() function along with it.

For example, let's say you have the following markup:

    <ul id="nav">
        <li>List item</li>
        <li>List item with sub items
            <ul>
                <li>Sub list item</li>
            </ul>
        </li>
    </ul>

This would select the last top-level <li>

$('ul#nav > li:last').css('border', '1px solid red');

---

This would select the last <li> traversing the DOM downward. In this case it's the <li> with text "Sub list item"

$('ul#nav li:last').css('border', '1px solid red');

---

This would select any <li> tags that are the last child of their parent

$('ul#nav li:last-child').css('border', '1px solid red');

Answer 2

var maintabs = $('.maintab'),
    active_maintab_eq = 0,
    active_subtab_number = 1;

$(document).keyup( function(e){

if (e.which == 39) {
// right arrow key pressed
    if ( active_subtab_number == maintabs.eq(active_maintab_eq).find('li').length ) {
        // go to next main-tab
        // and reset active sub-tab counter
        ++active_maintab_eq;
        active_subtab_number = 1;
    } else {
        ++active_subtab_number;
    }
}

});

Some thing like this, I guess.

Answer 3

You can use .length to find out if a jQuery selector found anything:

var nextSubTab = $(currentSubTab).next("li");
if (nextSubTab.length == 0) {
    // oops, end of this tab, switch to next tab
}