# Built-in Data Types
# Number
Represents integer & floating-point numbers.
let age: number = 25;
let price: number = 29.99;
let anotherNumber: number = 123_456_789;# String
Represent textual data.
let name: string = "John";# Boolean
Represents true/false values.
let isStudent: boolean = true;# Undefined
For variables, that have been declared but not assigned a value.
let undefinedVar: undefined;# Null
For variables, that clearly represents an absence of any object value.
let nullVar : null = null;# Any
Avoid using this type. With this type, you lose the static type feature.
let level;
level = 1;
// would be possible, the variable is considered as "any" type
level = "start";# Void
Return type of functions - that do not return a value.
function logMessage(): void {
console.log("Hello, Typescript!");
}# User-Defined Data Types
# Arrays
Allow you to store multiple values of the same type.
let numbers: number[] = [1, 2, 3, 4, 5, 6];# Enums
To organize & represent a set of named values.
// by default - .ts-compiler: Id of Red: 0, Green: 1, Blue: 2
// using a `const enum Color` - compiler generates more optimized code
enum Color {
Red,
Green,
Blue
}
let myColor: Color = Color.Green;# Classes
Provide a blueprint for creating objects with methods & properties.
class Person {
constructor(public name: string) {}
}
let person = new Person("Alice");# Interfaces
Define the structure of objects & can be used to enforce a specific shape on objects.
interface Shape {
area(): number;
}
class Circle implements Shape {
constructor(private radius: number) {}
area(): number {
return Math.PI * this.radius ** 2;
}
}# Tuple Data Type
Allow you to express an array where the type of fixed number of elements is known. Useful for key-value pairs.
let person: [string, number] = ["John", 30];# Object Data Type
Objects in TS can have a specific shape defined by interfaces or types.
interface Person {
name: string;
age: number;
}
let person: Person = { name: "John", age: 30 };# Custom Data Type
Cerating custom types using the type keyword.
type Point = { x: number; y: number };
let point: Point = { x: 10; y: 20 };# Class TypeScript
Classes are a fundamental part of oop in TypeScript.
class Animal {
constructor(public name: string) {}
makeSound(): void {
console.log("Some generic sound");
}
}
let dog = new Animal("Bello");
dog.makeSound(); // Output: Some generic sound