JSFiddle - React, Tailwind, and code Playground

HTML

<form>
    <input onclick="ATHD()" id="1" type="checkbox" name="pr" value="Password Reset" />&#160;Password Reset<br />
    <input onclick="ATHD()" id="2" type="checkbox" name="ps" value="Password Setup" />&#160;Password Setup<br />
    <input onclick="ATHD()" id="3" type="checkbox" name="fu" value="Firmware Upgrade (if applicable)" />&#160;Firmware Upgrade (if applicable)<br />
    <input onclick="ATHD()" id="4" type="checkbox" name="la" value="Local Access Setup" />&#160;Local Access Setup<br />
    <input onclick="ATHD()" id="5" type="checkbox" name="ra" value="Remote Access Setup" />&#160;Remote Access Setup<br />
    <input onclick="ATHD()" id="6" type="checkbox" name="ma" value="Mobile Access Setup" />&#160;Mobile Access Setup<br />
    <input onclick="ATHD()" id="7" type="checkbox" name="rss" value="Recording Schedule Setup" />&#160;Recording Schedule Setup<br />
    <input onclick="ATHD()" id="8" type="checkbox" name="pb" value="How to playback video" />&#160;How to playback video<br />
    <input onclick="ATHD()" id="9" type="checkbox" name="cv" value="How to convert video" />&#160;How to convert video<br />
    <input onclick="ATHD()" id="10" type="checkbox" name="en" value="Email Notification Setup" />&#160;Email Notification Setup<br />
    <input onclick="ATHD()" id="11" type="checkbox" name="ptz" value="PTZ Setup (if applicable)" />&#160;PTZ Setup (if applicable)<br />
    <input type="hidden" id="hdnValues" />
    <textarea id="showValues" row="10" cols="50"></textarea>
</form>

JavaScript

// find number of checkboxes (you haven't specified if you 
// have a set number or not. If you have a set number, just 
// set checkboxCount to whatever number you have.
var checkboxCount = 0;
var inputTags = document.getElementsByTagName('input');
for (var i=0, length = inputTags.length; i<length; i++) {
     if (inputTags[i].type == 'checkbox') {
         checkboxCount++;
     }
}

function ATHD() {
    var totalValue = '';
    for (var i = 1; i < checkboxCount; i++) {
        if (document.getElementById(i).checked)
            totalValue += inputTags[i].value + ';';
    }
    document.getElementById("hdnValues").value = totalValue;
    document.getElementById("showValues").value = totalValue;
}