JavaScript data types

<!    DOCTYPE html>//return NULL if object does not exist        //variable not assigned value is undefined        varTest1 = "ABCdef"; varTest2 = 123; varTest3 =true; varTest4 = {}; varTEST5 = []; varTest6; varTest7 = {"ABCdef": 123}; varTest8 = ["Abac", 123]; functionTest9 () {return"AVC"}; varTest10 =NULL; Console.log (typeoftest10)//nan is a numeric value that cannot be represented, cannot compare itself to Nan! = Nan, and nan is not equal to anything        //Judging Nan, any value that is not a number passed to isNaN returns the result that is true        varMyNum; if(IsNaN (MyNum)) {MyNum= 0;        } alert (MyNum); //infinity refers to a value that exceeds the upper or lower limit of the data        if(99 = = "99") {Console.log ("A number equals A string"); } Else{Console.log ("No" a number equals a strings "); }    </script>
JavaScript data types