JSFiddle - React, Tailwind, and code Playground

HTML

<input type="number" name="amount" min="4" max="6" step="2" value="4" id="amount" />

JavaScript

document.getElementById('amount').onkeypress = function(e) { e.preventDefault(); };

document.getElementById('amount').onkeydown = function(e) {
    if(e.keyCode != 38 && e.keyCode != 40)
        e.preventDefault();
};

if(document.addEventListener)
    document.getElementById('amount').addEventListener('contextmenu',function(e) { e.preventDefault();
},false);