JSFiddle - React, Tailwind, and code Playground

HTML

<p id="foo">&nbsp;</p>

<button onclick="
  document.getElementById('foo').innerHTML = nextWord();
">Update</button>
<button onclick="
  document.getElementById('foo').innerHTML = lastWord();
">last</button>

JavaScript

var wordArray = ['fe','fi','fo','fum'];
var count = -1;
var nextWord = function() {
    // silly work-around for negative modulus issue
    var index = (++count % wordArray.length) + wordArray.length
    return wordArray[index % wordArray.length];
};
var lastWord = function() {
    // silly work-around for negative modulus issue
    var index = (--count % wordArray.length) + wordArray.length
    return wordArray[index % wordArray.length];
};