Mundane Reddit Cry for Help

How can I make a button that evaluates everything on the page and works every time I press it?

JavaScript:
``
    function N() { let para = document.getElementsByClassName("TOKI")[0];
    if (para.classList.contains("S")) { para.classList.remove("S");
    }
    if (para.classList.contains("TOKI")) { para.classList.add("S"); }
    }``

HTML:

``
    <h1 class=TOKI>Heading</h1>
    <button onclick="N()">This button should toggle "S" for everything with the "TOKI" class.</button>
    <div class="TOKI framewords"><p>Body</p></div>
``