typescript.md

TypeScript cheat-sheet

What is TypeScript ?

TypeScript (TS) is a programming language. We use this programming language for large-scale JavaScript application development. We can refer to it as a typed superset of JavaScript.

🔗 https://www.typescriptlang.org/

How TypeScript work?

TypeScript language needs a compiler that can convert TypeScript syntax into standard JavaScript, this compiler is called a transpiler. Transpiler is designed to convert one programming language into another one.

TypeScript files come with .ts extension. Once transpiler compiles the .ts files, you will get .js files as output.

Cheat Sheets

Contents

• Type
• Type vs Interface
• Object Literal Syntax
• Interface
• Common Syntax
• Generics

📄 Type

Type vs Interface

• Interfaces can only describe object shapes.
• Interfaces can be extended by declaring it multiple times.
• In performance, Types can be faster.

Object Literal Syntax

type JSONResponse = {
  version: number; // Field
  payloadSize: number; // In bytes
  outOfStock?: boolean; // Optional
  update: (retryTimes: number) => void; // Arrow func field
  update(retryTimes: number): void; // Function
  (): JSONResponse; // Type is callable
  [key: string]: number; // Accepts any index
  new (s: string): JSONResponse; // Newable
  readonly body: string; // Readonly property
};

📄 Interface

Used to describe the shape of objects, and can be extended by others.

Common Syntax

interface JSONResponse extends Response, HTTPAble = {
  version: number;
  payloadSize: number; // In bytes
  outOfStock?: boolean; // Optional
  ...
};

extends Response, HTTPAble Optionally take properties from existing interfaces or types.

Generics

Declare a type which can change according to your interface

interface APICall<Response> = {
  data: Response;
};