Q
What is the difference between 'Undefined' and 'Null' in JavaScript?

Answer & Solution

Answer: Option B
Solution:
Undefined represents variables that have been declared but not initialized, while Null represents an intentional absence of value or object reference.
Related Questions on Average

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'.

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 is an example of using 'Null' in JavaScript?

A). let user = null;

B). let user = undefined;

C). let user;

D). let user = '';

When does the JavaScript engine assign an 'Undefined' value to a variable?

A). When the variable is intentionally set to 'Undefined'.

B). When the variable is not declared but used.

C). When the variable is declared but not initialized.

D). When the variable is initialized with the value 'Undefined'.

What does the expression null == undefined return in JavaScript?

A). 1

B). 0

C). undefined

D). null

What is the purpose of using 'Null' over 'Undefined' in certain programming scenarios?

A). To represent an intentional absence of value or object reference.

B). To assign default values to variables.

C). To represent uninitialized variables.

D). To check for variable existence.

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'.

What happens when a function does not explicitly return a value in JavaScript?

A). It returns 'null'.

B). It returns 'undefined'.

C). It throws an error.

D). It returns 'object'.

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.

What does the expression typeof null return in JavaScript?

A). null

B). object

C). undefined

D). function