How do I fix my code about a script that stopped working?

I have this code that generates an item code when the ‍combo-boxes‍‍‍ are selected.

For example, if Computer Equipment and Printer is selected, the script would generate the code ‍CEPR000001‍ and display it on the textbox. It was working last March but now it suddenly stopped working. Can someone help me with this?

Script:

function pad(num, size) {
    var s = num+"";
    while (s.length < size) s = "0" + s;
    return s;
}

function getAssetCode() {
    document.getElementById("code2").value = $('#class').find(":selected").data('value') + 1;

    var x = document.getElementById("cat").value;
    var y = document.getElementById("class").value;
    var z = document.getElementById("code2").value;         

    var result = pad(z, 6);

    var xyz = x.concat(y,result);

    $('#code').value(xyz);
}

HTML:

<select class="form-control" name="assetcategory" id="cat" required>
    <option value="CE">Computer Equipment</option>
    <option value="OP">Other Properties</option>
</select>

<select class="form-control" name="assetclass" id="class" onchange="getAssetCode()" required>
    <option value="PR" data-value="1">Printer</option>
    <option value="CP" data-value="2">Mobile Phone</option>
</select>

<input type="text" class="form-control" name="assetcode1" id="code" disabled>
<input type="text" class="form-control" name="assetcode2" id="code2" hidden>