JSFiddle - React, Tailwind, and code Playground

HTML

<input type='textbox' onkeydown="validate(event)"/>

JavaScript

function validate(evt) {
    var theEvent = evt || window.event;
    var key = theEvent.keyCode || theEvent.which;
    key = String.fromCharCode(key);
    if (!/-?\d+/.test(key)) {
        console.log(key);
        evt.stopPropagation();
        evt.preventDefault();  
        evt.returnValue = false;
        evt.cancelBubble = true;
        return false;
    }
}