JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" onkeypress='return validateQty(event);'>

JavaScript

function validateQty(event) {
    var key = window.event ? event.keyCode : event.which;
if (event.keyCode == 8 || event.keyCode == 46
 || event.keyCode == 37 || event.keyCode == 39) {
    return true;
}
else if ( key < 48 || key > 57 ) {
    return false;
}
else return true;
};