Use the CSS : valid selector to style all <input> elements with a valid value .
Example
You can try to run the following code to implement the :valid Selector
<!DOCTYPE html>
<html>
<head>
<style>
input:valid {
background: red;
color: white;
}
</style>
</head>
<body>
<h2>Heading</h2>
<input type = "email" value = "[email protected]">
<p>The style (red color background) appears if you type a relevant/ valid email address.</p>
</body>
</html>