How to check if an object is an Array or not?

What is the output of the following code?

var x = 20;
{
var x = 21;
}

Which of the following variable declaration keywords will have the same scope as 'let'?

Which is the method used to add an event listener?

JavaScript entities start with & and end with ;

What will be the output of the following JavaScript function?

What is the advantage of the code produced graphics being smaller than the images themselves?

Identify the React hook which customizes the instance value that is exposed to parent components when using ref.

In the following switch syntax, the expression is compared with the case labels using which of the following operator(s)?

 switch(expression)

 {   

        statements

 } 

The snippet that filters the filtered set is _____