JSFiddle - React, Tailwind, and code Playground

HTML

<p>Search: <input type="text" name="questioncontent" onblur="fnValidatePAN(this)" /></p>

JavaScript

function fnValidatePAN(Obj) {
        if (Obj == null) Obj = window.event.srcElement;
        if (Obj.value != "") {
            ObjVal = Obj.value;
            var panPat = /^([a-zA-Z]{5})(\d{4})([a-zA-Z]{1})$/;
            var code = /([C,P,H,F,A,T,B,L,J,G])/;
            var code_chk = ObjVal.substring(3,4);
            if (ObjVal.search(panPat) == -1) {
                alert("Invalid Pan No");
                Obj.focus();
                return false;
            }
            if (code.test(code_chk) == false) {
                alert("Invaild PAN Card No.");
                return false;
            }
        }
   }