Which operator is used to test if a particular property exists or not?

Which of the following is not a valid JavaScript identifier?

Which method is used to connect the last vertex back to the first?

In the following syntax, the data type within the square brackets must be:

What will be the output of the following JavaScript code?

function myFunction()
{
   document.getElementById("demo").innerHTML = Boolean(10 > 9);
}

What is the observer effect?

  The statement a===b refers to _________ 

If a window has child windows, how will the browsing histories be affected?

What is being used to ensure that each subset conforms to the subset?