JSFiddle - React, Tailwind, and code Playground

HTML

<form id="formElement">
    One: <input type="text"><br>
    Two: <input type="text">
</form>

CSS

.focused {
    outline: solid 2px red;
}

JavaScript

var formElement = document.forms['formElement'];

formElement.onfocus = function(evt) {
    var activeElement = formElement.querySelector('.focused');
	if (activeElement) {
	    activeElement.classList.remove('focused');
    }
    evt.target.classList.add('focused');
};

formElement.onblur = function(evt) {
	var activeElement = formElement.querySelector('.focused');
    if (activeElement) {
     	activeElement.classList.remove('focused');   
    }
};