JSFiddle - React, Tailwind, and code Playground

HTML

<input id='promo' type='text' />
<div id='submit' class='button'>Submit</div>
<div id='hidden' class='button'>Hidden</div>

CSS

.button {
  display: inline-block;
  border: 1px solid;
  border-radius: 5px;
  background-color: lavender;
  padding: 0 5px 0 5px;
  user-select: none;
  cursor: pointer;
}

#hidden {
  display: none;
}

JavaScript

window.addEventListener('DOMContentLoaded', () => {


  document.getElementById('submit').addEventListener('click', () => {
  	const val = Number(document.getElementById('promo').value);
    if (!isNaN(val) && val >= 100 && val <= 200) {
    	document.getElementById('hidden').setAttribute("style", "display: inline-block;");
    }
	});
});