<!doctype html>

<html lang="en">

<head>

<meta charset="utf-8">

<title>addClass</title>

<style>

p {

margin: 8px;

font-size: 16px;

}

.selected {

color: rgb(99, 187, 182);

}

.highlight {

background: yellow;

}

</style>

<script src="https://code.jquery.com/jquery-3.4.1.js"></script>

</head>

<body>

<p>Hello</p>

<p>and</p>

<p>Goodbye</p>

<script>

$("p").last().addClass("highlight");

// $("p").last().addClass("selected");

</script>

</body>

</html>