arrow keys navigation through li (no jquery)

Question

I'm trying to figure out a way to create an extremely basic autocomplete without 3rd parties dependencies. so far I've gotten to populate a list of results with an ajax call, and with mouse onclick events on each li the script completes the fields as supposed.
what I need to implement is an up/down/enter keys navigation system based on pure js, and after hours spent searching I gave up. this fiddle explains quite perfectly my situation, with the difference that it does require jQuery.

I'd rather not paste any of my own code here as the final aim is learning the process, but since I'm linking to jsfiddle I'm required to so here's the fiddle.

fiddle HTML:

<div id="MainMenu">
    <ul>
        <li class="active"><a href="#">PATIENT TEST</a></li>
        <li><a href="#">QC TEST</a></li>
        <li><a href="#">REVIEW RESULTS</a></li>
        <li><a href="#">OTHER</a></li>
    </ul>
</div>

<a href="#" id="btnUp">Up</a>
<a href="#" id="btnDown">Down</a>

fiddle JS:

$(document).ready(function () {
    $('#btnDown').click(function () {
        var $current = $('#MainMenu ul li.active');
        if ($current.next().length > 0) {
            $('#MainMenu ul li').removeClass('active');
            $current.next().addClass('active');
        }
    });

    $('#btnUp').click(function () {
        var $current = $('#MainMenu ul li.active');
        if ($current.prev().length > 0) {
            $('#MainMenu ul li').removeClass('active');
            $current.prev().addClass('active');
        }
    });

    $(window).keyup(function (e) {
        var $current = $('#MainMenu ul li.active');
        var $next;

        if (e.keyCode == 38) {
            $next = $current.prev();
        } else if (e.keyCode == 40) {
             $next = $current.next();
        }

        if ($next.length > 0) {
            $('#MainMenu ul li').removeClass('active');
            $next.addClass('active');
        }
    });

});

thanks a lot in advance to anyone willing to point me in the right direction.

Answer 1

This turned out to be simpler than I expected, and I've came up with the following code which appearently does the job quite well.

Things to take in account are:

• the HTML attribute 'tabindex' must be specified on each element for the .focus() to be applied
• to have a ENTER->submit feeling, you MUST target a link element within the li (still, I'm achieving this with onclick events not included here)
• this works with an extremely simple list structure, so far I haven't tested it with nested dropdown menus
• this is most likely not suitable for a copy/paste situation, but as far as I can tell this method is procedurally currect, and can get you started developing more complex solutions 这很可能不适合复制/粘贴情况，但据我所知，这种方法是程序性的，并且可以让您开始开发更复杂的解决方案

This is the basic HTML:

<input type="text" name="main_input" id="input" />
<ul id="list">
 <li class="listElement"><a href="#" tabindex="1">li content</a></li>
 <li class="listElement"><a href="#" tabindex="1">li content</a></li>
 <li class="listElement"><a href="#" tabindex="1">li content</a></li>
</ul>

And here's the JS function, triggered when the list above is populated and shown:

    function scrollList() {
      var list = document.getElementById('list'); // targets the <ul>
      var first = list.firstChild; // targets the first <li>
      var maininput = document.getElementById('input');  // targets the input, which triggers the functions populating the list
      document.onkeydown = function(e) { // listen to keyboard events
        switch (e.keyCode) {
          case 38: // if the UP key is pressed
            if (document.activeElement == (maininput || first)) { break; } // stop the script if the focus is on the input or first element
            else { document.activeElement.parentNode.previousSibling.firstChild.focus(); } // select the element before the current, and focus it
            break;
          case 40: // if the DOWN key is pressed
            if (document.activeElement == maininput) { first.firstChild.focus(); } // if the currently focused element is the main input --> focus the first <li>
            else { document.activeElement.parentNode.nextSibling.firstChild.focus(); } // target the currently focused element -> <a>, go up a node -> <li>, select the next node, go down a node and focus it
          break;
        }
      }
    }

Apologies in advance for the kinda chaotic layout of the code, the function I came up with is a bit more complex and I've stripped out most of it for explaination purposes.

Needless to say, I'm looking forward any comment about the solution above, in regard of errors, improvements or known compatibility issues.

Answer 2

you wrote

tabindex="1"

Why not just tabindex="0"? Using a positive umber greater than 0 is only needed if you want to cahnge the default order of navigation.