Types

Lecture Overview

• What are types
• Why types matter
• Examples of types

What are types?

• JavaScript variables can hold different data types:
  • booleans
  • numbers
  • strings
  • functions
  • objects, and more

What Effect Do Types Have?

• The type of a variable dictates the way that you can interact with it.
• For example, you cannot divide a string type, because it is text.
  • However, you can divide integer types because it is a number.

How to Identify Type?

• The typeof operator is used to identify the type of a variable.
• The typeof operator returns the type of a variable or an expression

typeof Example

let age = 28;
console.log(typeof age)

The sample script above produces the output below

number

JavaScript Booleans

• Booleans can only have two values: true or false.
• Booleans are used in conditional testing and controlling the flow of data in an application.

Number Types

• There are usually two types of numbers: integers, and floating points.
• Integers are whole numbers, with no decimal value.
• Floating are decimal values.
• JavaScript recognizes both types as Number types

Number Example

let age = 28;
let averageHeight = 67.5
let typeOfAge = typeof(age)
let typeOfAverageHeight = typeof(averageHeight)
console.log(typeOfAge)
console.log(typeOfAverageHeight)

The sample script above produces the output below

number
number

Textual Type

• There are usually two types of texts: characters and string (or text string).
  • A character (or a text string) is a single character wrapped in single quotes, ', like 'a'.
  • A string (or a text string) is a series of characters wrapped in double quotes, ", like "John Doe".
• JavaScript recognizes both types as string types

String Example

let age = "28";
let averageHeight = "67.5"
let typeOfAge = typeof(age)
let typeOfAverageHeight = typeof(averageHeight)
console.log(typeOfAge)
console.log(typeOfAverageHeight)

The sample script above produces the output below

string
string