Primitive data types in Javascript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are primitive data types in JavaScript?

Primitive data types are the most basic data types in JavaScript. They represent simple values and are not objects. Examples include string, number, boolean, null, undefined, symbol, and bigint.

beginner

What is the difference between null and undefined?

null means a variable has been explicitly set to have no value. undefined means a variable has been declared but not assigned any value yet.

beginner

Which primitive data type is used to represent true or false values?

The boolean data type represents logical values: true or false.

intermediate

What is a symbol in JavaScript?

A symbol is a unique and immutable primitive value often used to create unique object property keys to avoid name conflicts.

intermediate

How do you create a BigInt value in JavaScript?

You create a BigInt by appending n to the end of an integer literal, for example: 123n. BigInt is used for integers larger than the Number type can safely represent.

Which of the following is NOT a primitive data type in JavaScript?

A Boolean

B String

C Object

D Symbol

Objects are not primitive data types; they are complex data types that can hold multiple values.

What value does an uninitialized variable hold in JavaScript?

A undefined

B false

C 0

D null

An uninitialized variable holds the value undefined.

Which primitive type would you use to store the text 'Hello'?

A String

B Number

C Boolean

D Symbol

Text values are stored as String primitive type.

How do you create a BigInt literal?

A By calling BigInt() without arguments

B By writing a number with a decimal point

C By using quotes around a number

D By appending 'n' to an integer

Appending 'n' to an integer creates a BigInt literal, e.g., 9007199254740991n.

Which primitive type is used to represent a unique identifier?

A Boolean

B Symbol

C Null

D Undefined

Symbol is used to create unique identifiers.

Explain the main primitive data types in JavaScript and give a simple example of each.

Think about the simplest values you can store in variables.

Describe the difference between null and undefined in JavaScript.

Consider what happens when you declare a variable but don’t assign it.