countUp.html

<h1>The results of the function are:</h1>

<p id="fill"></p>

countUp.js

var theDiv = document.getElementById("fill");

function countUp() {
    var i = 0;
    var result = "";
    for (i = 1; i < 100; i++) {
        if (i % 5 === 0) {
            if (i % 3 === 0) {
                result = "threefive";
            } else {
                result = "five";
            } 
        } else if (i % 3 === 0) {
            result = "three";
        } else {
            result = i.toString();
        } 
       theDiv.innerHTML += result;
       theDiv.innerHTML += "<br/>";
    }
}

countUp();