Getting started · Lesson 3 of 45

Data types

The 8 types, and how to tell a value's type.

8 minutes4 games

Every value has a type. There are 7 simple types (primitives) and one complex one:

string: text, "hello".
number: whole or decimal, 42, 3.5.
boolean: true or false.
undefined: a variable with no value yet.
null: “no value” on purpose.
bigint: huge whole numbers, 9007199254740993n.
symbol: a unique value, rarely needed.
object: anything composite: objects, arrays and functions.

JavaScript

console.log(typeof "SeaCode")
console.log(typeof 2026)
console.log(typeof true)
let nothing
console.log(typeof nothing)
console.log(typeof [1, 2])
console.log(typeof null)

What's the output?

console.log("5" + 1)
console.log(5 + 1)

What will this code print?

Quick question

What does typeof false return?

Order the lines

Order the lines so the code prints number.

Click the lines in the right order

Exercise

Print the type of 3.14.

Expected output: number

JavaScript

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JavaScript

Getting started · Lesson 3 of 45

Data types

The 8 types, and how to tell a value's type.

8 minutes4 games

Every value has a type. There are 7 simple types (primitives) and one complex one:

string: text, "hello".
number: whole or decimal, 42, 3.5.
boolean: true or false.
undefined: a variable with no value yet.
null: “no value” on purpose.
bigint: huge whole numbers, 9007199254740993n.
symbol: a unique value, rarely needed.
object: anything composite: objects, arrays and functions.

JavaScript

console.log(typeof "SeaCode")
console.log(typeof 2026)
console.log(typeof true)
let nothing
console.log(typeof nothing)
console.log(typeof [1, 2])
console.log(typeof null)

What's the output?

console.log("5" + 1)
console.log(5 + 1)

What will this code print?

Quick question

What does typeof false return?

Order the lines

Order the lines so the code prints number.

Click the lines in the right order

Exercise

Print the type of 3.14.

Expected output: number

JavaScript

Learn more from

Played 0 of 4 games