Safe AND quickest way to add a css class to the body of the DOM

document.body.className += ' home';

Performance comparision: className vs classList vs addClass :

Update(based on PSL's comment)

or for newer ones document.body.classList.add("home");

Make sure you do this under the <body>, it won't work if applied from a <head> script

Right after the opening body tag, you can create a script tag :

<body>
<script>
    $('body').addClass('home')
</script>
<!-- HTML content bellow -->
</body>

The only condition is that the jQuery is loaded in the head.

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