The Modern JavaScript Bootcamp (2019) - Undefined and Null

This video tutorial introduces the concepts of undefined and null in JavaScript. It explains how undefined is used to represent the absence of a value in variables, function arguments, and return values. The tutorial also covers how null can be used to explicitly clear a variable's value, differentiating it from undefined. Through examples, the video demonstrates how these concepts are applied in JavaScript programming.

What do undefined and null represent in JavaScript?

• A type of function

• A type of error

• A type of loop

• The absence of a value

What happens when a variable is declared but not assigned a value in JavaScript?

• It is assigned the value zero

• It is assigned the value undefined

• It causes a syntax error

• It is assigned the value null

In JavaScript, what value is assigned to a function argument if no value is provided?

• zero

• undefined

• an empty string

• null

What is the default return value of a function in JavaScript if no return statement is used?

• an empty string

• zero

• undefined

• null

How can a developer explicitly clear a variable's value in JavaScript?

• Assign it the value null

• Assign it the value zero

• Assign it the value undefined

• Assign it an empty string

What is the key difference between undefined and null in JavaScript?

• Undefined is a language default, null is explicitly set by developers

• Null is a language default, undefined is explicitly set by developers

• Both are language defaults

• Both are explicitly set by developers

When should null be used instead of undefined in JavaScript?

• When a variable is declared but not assigned

• When a function does not return a value

• When a developer wants to explicitly clear a variable's value

• When a function argument is not provided