Getting unexpected behaviour with firefox web console, equality for undefined not working fine : <p>When trying to write following javascript code snippet in mozilla web console then getting following unexpected behaviour.Please refer below image.When I declared a variable x then the undefined check evaluated to true.But when I defined it as "var a" then I get a seemingly wrong answer.I have checked it for chrome it is working fine.Can please someone explain this obscure behaviour?</p>

<p><a href="https://i.stack.imgur.com/S56rn.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/S56rn.png" alt="enter image description here"></a></p>
