JSFiddle - React, Tailwind, and code Playground

HTML

<div id="speed"></div>

JavaScript

function speedcounter() {
document.getElementById('speed').innerHTML = "";
var spx;
var speed = 3;
var sp=["0","3","4","4","4","5","6","7","8"];

document.getElementById('speed').innerHTML += '<h2>Speed</h2></br>';
document.getElementById('speed').innerHTML += '<input type="button" onclick="addspeed();" value="+"><br />';

 for (spx=8; spx>=0; spx--) {
    if (spx == speed) { 
        document.getElementById('speed').innerHTML += '<span style="color:#00FF00">' + sp[spx] + '</span><br />';
    } else {
        document.getElementById('speed').innerHTML += sp[spx] + "<br />"; 
    }
 }
 document.getElementById('speed').innerHTML += '<input type="button" onclick="remspeed();" value="-">';    
}

speedcounter();