Introduction

• TS or TypeScript is a programming language that compiles to JavaScript
• It is a superset of JavaScript, so any valid JavaScript code is valid TypeScript code
• Benefits:
  • Tooling: catch bugs while coding in your editor
  • You can work with types, interfaces, generics, ...
  • Write most recent JavaScript features and transpile them to the JS version you want to use
• Goals:
  • Provide an optional type system for JavaScript
  • Provide planned features from future JavaScript editions to current JavaScript engines

Type system

• Why add types to JavaScript?
  • Allows compiler to catch errors while coding
  • Types increase the readability of your code
  • Great form of documentation

Your JavaScript is TypeScript

• TypeScript provides compile time type safety for your JavaScript code
• Types are completely optional!
• You can simply change the .js extension to .ts
• TypeScript is intentionally and strictly a superset of JavaScript with optional type checking

Types can be implicit

• Even if you don't explicitly define a type, TypeScript will infer it:

let foo = 123;
foo = '456'; // Compile error: cannot assign `string` to `number`

// Is foo a number or a string?

Types can be explicit

• You can explicitly define a type:

let foo: number = 123;