Summary - Variables and types

JavaScript course · Beginner · Lesson 6/133

Combine variable declaration and data types to write a small profile card.

Summary - Variables and types

In this unit you learned to declare variables in JavaScript. With let you declare changing values, with const fixed values; var is old style. You print values to the screen with console.log.

You met the three core primitive types: number, string and boolean. null is an intentional empty value, undefined is an unassigned value. You checked types with typeof and saw the typeof null "object" pitfall.

Exercise Write a profile card

Declare three variables: ad (a name, string), yas (an age, number), aktif (is the user active, boolean). Then print all three together with console.log.

Show example solution

const ad = "Alex";
const yas = 28;
const aktif = true;
console.log(ad, yas, aktif);

Exercise Print a variable's type with typeof

Declare a variable (example: a city name). Then find its type with typeof and print it with console.log.

Show example solution

let sehir = "Berlin";
console.log(typeof sehir);

Test yourself

Which operator finds a variable's type?
- type
- typeof
- kindof
- dtype
Show answer

typeof — Correct. The typeof operator returns a value's type as a string.
Match concepts to their descriptions

let

Value can change
const

Cannot be reassigned
null

Intentional empty
typeof

Tells the type

All lessons in Beginner

1 Variables and data types

2 Operators

3 Conditionals

Summary - Variables and types