Onclick event in javascript

W jaki sposób dodać onclick event do dowolnego elementu na stronie?

Dodanie onclick event dla przycisku na stronie

<!DOCTYPE html>
<html lang="pl">
<head>
    <meta charset="UTF-8">
    <title>Page Title</title>
    <meta name="viewport" content="width=device-width,initial-scale=1">
    <link rel="stylesheet" href="style.css">
</head>
<body>
    <div class="main_title">Main title</div>
    <p class="intro">This is an intro</p>
    <button onclick="this.textContent = 'Clicked!'">Click me</button>

    <script type="text/javascript" src="main.js"></script>
</body>
</html>

Wywołanie funkcji po kliknięciu na jakikolwiek elelment na stronie

<!DOCTYPE html>
<html lang="pl">
<head>
    <meta charset="UTF-8">
    <title>Page Title</title>
    <meta name="viewport" content="width=device-width,initial-scale=1">
    <link rel="stylesheet" href="style.css">
</head>
<body>
    <div class="main_title">Main title</div>
    <p onclick="changeText(this)" class="intro">This is an intro</p>
    <button onclick="changeText(this)">Click me</button>

    <script type="text/javascript" src="main.js"></script>
</body>
</html>

function changeText(arg){
    arg.textContent = "Clicked!!!";
}