JSFiddle - React, Tailwind, and code Playground

HTML

<div id="navigation">
    <div class="navlinks">
        <div id="output2">
            <ul class="mainMenu">
                <li class="mmenu-item-0"> <a href="http://www.thegaminghideout.com/About.html">About</a>

                </li>
                <li class="mmenu-item-1"> <a href="http://www.thegaminghideout.com/Games.html">Games</a>

                </li>
                <li class="mmenu-item-2"> <a href="http://www.thegaminghideout.com/The Hideout.html">The Hideout</a>

                </li>
                <li class="mmenu-item-3"> <a href="http://www.thegaminghideout.com/Staff.html">Staff</a>

                </li>
                <li class="mmenu-item-4"> <a href="http://www.thegaminghideout.com/Donate.html">Donate</a>

                </li>
                <li class="mmenu-item-5"> <a href="http://www.thegaminghideout.com/Contact Us.html">Contact Us</a>

                </li>
            </ul>
        </div>
    </div>
    <br>
    <br>
    <br>
    <button onclick="removeLinks()">Remove Links</button>
    <button onclick="execFunction()">Link Set 1</button>
    <button onclick="execFunction2()">Link Set 2</button>

CSS

#navigation {
    width: 760px;
    height: 35px;
    position: absolute;
    border-bottom: 2px solid #000000;
    background: orange;
    padding: 0px;
}
#navigation .padding {
    padding: 2px;
}
#navigation .navlinks {
    position: absolute;
    top: 1px;
    left: 0px;
}
#navigation .navlinks ul {
    margin: 0px;
    padding: 0px;
    text-align: center;
    list-style-type: none;
    width: 760px;
    height: 35px;
}
#navigation .navlinks li {
    position: relative;
    top: 5px;
    margin: 0px 5px 0px 5px;
    list-style-type: none;
    display: inline;
}
#navigation .navlinks li a {
    color: #000000;
    padding: 5px 0px 9px 0px;
    text-decoration: none;
    font-size: 18px;
    font-family: karmatic_arcaderegular;
    padding: 5px 0px 9px 0px;
}
#navigation .navlinks li a:hover {
    margin: 0px;
    color: #ffffff;
    background: orange;
    text-decoration: underline;
}

JavaScript

function execFunction() {
    removeLinks();
    linksAddSet1();
}

function execFunction2() {
    removeLinks();
    linksAddSet2();
}

function removeLinks() {
    var list = document.getElementById("output2");
    while (list.hasChildNodes()) {
        list.removeChild(list.lastChild);
    }
}

function linksAddSet1() {
    var out = document.getElementById("output2");
    var args = ["About", "Games", "The Hideout", "Staff", "Donate", "Contact Us", ];

    function displayMenu() {
        var ul = document.createElement('ul');
        ul.className = "mainMenu";
        args.forEach(function (name, index) {
            var li = document.createElement('li'),
                an = document.createElement('a');
            li.className = "mmenu-item-" + index;
            li.setAttribute = "link rel", "stylesheet", "type", "text/css", "href", "http://www.thegaminghideout.com/style.css";
            an.innerHTML = name;
            an.setAttribute('href', "http://www.thegaminghideout.com/" + name + ".html");
            li.appendChild(an);
            ul.appendChild(li);
        });
        out.appendChild(ul);
    }
    if (output2.childNodes.length > 0) {} else {
        displayMenu();
    }
}

function linksAddSet2() {
    var list = document.getElementById("output2");
    var out = document.getElementById("output2");
    var args = ["Tools", "Tutorials"];

    function displayMenu() {
        var ul = document.createElement('ul');
        ul.className = "mainMenu";
        args.forEach(function (name, index) {
            var li = document.createElement('li'),
                an = document.createElement('a');
            li.className = "mmenu-item-" + index;
            li.setAttribute = "link rel", "stylesheet", "type", "text/css", "href", "http://www.thegaminghideout.com/style.css";
            an.innerHTML = name;
            an.setAttribute('href', "http://www.thegaminghideout.com/" + name + ".html");
            li.appendChild(an);
           ...