JSFiddle - React, Tailwind, and code Playground
by Akram kamal
HTML
<body>
<input type="text" placeholder="FirstField" name="firstfield" id="firstfield"/>
<input type="checkbox" name="for_advanced" id="for_advanced" onclick="validation()" />
<div class="no-display" id="for_hidden">
<input type="text" placeholder="SecondField" name="firstfield" id="firstfield"/>
<input type="text" placeholder="ThirdField" name="thirdfield" id="thirdfield"/>
</div>
</body>
CSS
.no-display{display:none;}
JavaScript
function validation()
{
var checkbox = document.getElementById("for_advanced");
if(checkbox.checked)
document.getElementById("for_hidden").className = "";
else
document.getElementById("for_hidden").className = "no-display";
}