Вот пример:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>If</title>
<style>
body{
margin: 0;
font-family: 'Courier New', Courier, monospace;
padding: 50px;
}
.settings{
display: flex;
align-items: center;
}
</style>
</head>
<body>
<p class="text">Привет!</p>
<div class="settings">
<p class="style">Жирный текст</p>
<input onchange="event.target.checked ? document.querySelector('.style').style.fontWeight = 900 : document.querySelector('.style').style.fontWeight = 400" type="checkbox">
</div>
<div class="settings">
<p class="italic">Наклонный текст</p>
<input onchange="event.target.checked ? document.querySelector('.italic').style.fontStyle = 'italic' : document.querySelector('.italic').style.fontStyle = 'normal'" type="checkbox">
</div>
</body>
</html>
