JSFiddle - React, Tailwind, and code Playground

HTML

<li id="2" onclick="register_click(1)">List item 1</li>
<li id="3" onclick="register_click(2)"></li>
      <li id="4"onclick="register_click(3)">Unit not showing any sign of life all LEDs are off.</li>

<input type='text' size="150%" width="100%" maxlength="" id="boxclicked">

JavaScript

function register_click(num){
document.getElementById('boxclicked').value = num; 

}