JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="theNumber"name="theNumber"size="3" onkeyup="return goodchars('theNumber','012345678');">

JavaScript

function getkey(e){
        if(window.event)
            return window.event.keyCode;
        else if(e)
            return e.which;
        else
            return null;
    }

    function goodchars(e, goods){
        console.log('e:'+e+', goods:'+goods);
        var key, keychar;
        key=getkey(e);
        console.log('e:'+e+', key:'+key);
        if(key==null) return true;
        keychar=String.fromCharCode(key);
        keychar=keychar.toLowerCase();
        goods=goods.toLowerCase();
        if(goods.indexOf(keychar)!=-1)
        return true;
        return false;
    }