How do you check if a variable has an "Undefined" value in JavaScript?

Which of the following is an example of using 'Null' in JavaScript?

A). let user = null;

B). let user = undefined;

C). let user;

D). let user = '';

When does a variable typically have an 'Undefined' value?

A). When it is intentionally set to represent no value.

B). When it is assigned a default value.

C). When it is declared but not initialized.

D). When it is explicitly set to 'Undefined'.

How is 'Null' different from 'Undefined'?

A). Null represents variables that have been initialized but not declared.

B). Null represents an intentional absence of value or object reference.

C). Null is never used in programming.

D). Null is a substitute for 'Undefined'.

How does the typeof operator behave when applied to an 'Undefined' value?

A). It returns 'undefined'.

B). It returns 'null'.

C). It throws an error.

D). It returns 'object'.

Which of the following statements is correct regarding the comparison of 'Undefined' and 'Null'?

A). Undefined and Null are strictly equal in JavaScript.

B). Undefined and Null are not strictly equal in JavaScript.

C). Undefined is considered a subtype of Null.

D). Null is considered a subtype of Undefined.

Which statement best describes the relationship between 'Undefined' and 'Null' in JavaScript?

A). Undefined and Null are interchangeable and can be used interchangeably in code.

B). Undefined and Null are distinct values representing different states in JavaScript.

C). Undefined is a subset of Null, encompassing all possible values of Null.

D). Null is a subset of Undefined, encompassing all possible values of Undefined.

What is the result of the expression typeof undefinedVariable if undefinedVariable is not declared?

A). object

B). function

C). undefined

D). null

Which of the following correctly describes the purpose of 'Null' in JavaScript?

A). Null is used to represent an empty array.

B). Null is used to indicate that a variable is uninitialized.

C). Null is used to represent an intentional absence of value.

D). Null is used to check for object properties.

Which of the following scenarios is a common cause of variables having an 'Undefined' value?

A). When variables are explicitly set to 'Undefined'.

B). When variables are declared but not initialized.

C). When variables are intentionally set to 'Null'.

D). When variables are assigned default values.

Which statement is true regarding the use of 'Undefined'?

A). Undefined is commonly used to reset variables in loops.

B). Undefined is generally avoided and considered a programming error.

C). Undefined is used to represent empty strings.

D). Undefined is only used in function declarations.