Question

Why is the following line not alerted?

  <script>
  alert(x);//this line is not executed or alerted  ???.It should have alerted "undefined" 
  console.log(x)//reference error 
  var y="maizere";
  alert(y);//this line is also not executed or alerted  ???

  </script>

Any undeclared variables are treated as global variable in javascript right?

Answer 1

alert(x);//this line is not executed or alerted  ???.It should have alerted "undefined" 

That’s incorrect. This line raises a ReferenceError because there’s no variable x.

Contrast this with situation:

var obj = {};
alert(obj.x); // undefined - there's no attribute x