JSFiddle - React, Tailwind, and code Playground
HTML
Experience: <span id="exp">0</span>
<br/>Level: <span id="level">0</span>
<br/>
<br/>
<button onclick="increment();">Increment</button>
JavaScript
var exp = 0,
level = 0;
function increment() {
exp++;
document.getElementById("exp").innerHTML = exp;
if (exp == 100) {
level = level + 1;
exp = 0;
document.getElementById("level").innerHTML = level;
}
}