JSFiddle - React, Tailwind, and code Playground

CSS

*{margin:0;padding:0;}
        #brd{margin:15px auto;}
        #brd,#brd td,#log{border:1px solid #000;}
        #brd td{height:47px;width:45px;text-align:center;font-size:30px;}
        #brd span{font-size:12px;}
        #log{margin:15px auto;padding:20px;width:385px;max-height:150px;overflow:auto;background:#F0F0F0;color:#000;}

JavaScript

var i,sdk,rem,log,perf,brd,bxes=[["11","12","13","21","22","23","31","32","33"],["14","15","16","24","25","26","34","35","36"],["17","18","19","27","28","29","37","38","39"],["41","42","43","51","52","53","61","62","63"],["44","45","46","54","55","56","64","65","66"],["47","48","49","57","58","59","67","68","69"],["71","72","73","81","82","83","91","92","93"],["74","75","76","84","85","86","94","95","96"],["77","78","79","87","88","89","97","98","99"]];

        /*Array Find*/
        function arrFind(fnd,frm,bol){
            var ii,len,rtn=-1;

            for(ii=0,len=frm.length;ii<len;ii++){
                if(frm[ii]==fnd){
                    rtn=ii;
                    break;
                }
            }
            return bol?rtn>-1:rtn;
        }

        /*To RC*/
        function toRC(val){
            var ii,len,aa=[];

            val=val.split(",");

            for(ii=0,len=val.length;ii<len;ii++){
                aa.push(Math.ceil((parseInt(val[ii])+1)/9)+""+((parseInt(val[ii])%9)+1));
            }

            return aa.join(",");
        }

        /*To AV*/
        function toAV(rc){
            var ii,len,aa=[];

            rc=rc.split(",");

            for(ii=0,len=rc.length;ii<len;ii++){
                aa.push((((parseInt(rc[ii].charAt(0))-1)*9)+(parseInt(rc[ii].charAt(1))-1))+"");
            }

            return aa.join(",");
        }

        /*Get Box*/
        function getBox(av,bol){
            var ii,jj,len,ss,zz,aa=[];

            if(!bol){
                av=toRC(av);
            }

            av=av.split(",");

            for(ii=0,len=av.length;ii<len;ii++){
                ss=av[ii];
                for(jj=0;jj<9;jj++){
                    zz=window.bxes[jj];
                    if(arrFind(ss,zz,true)){
                        aa.push(zz);
                        break;
                    }
                }
            }

            return aa.join(",");
        }

        /*Get Row*/
        function...