JSFiddle - React, Tailwind, and code Playground

by Blender

HTML

<input type="text" id="quant" value="0">
<button onclick="inc()">increase</button>
<button onclick="dec()">decrease</button>

JavaScript

function inc() {
    document.getElementById('quant').value++;
}

function dec() {
    document.getElementById('quant').value--;
}