TypeScript is an open-source language which builds on JavaScript, one of the world’s most used tools, by adding static type definitions. - Home / online

see also

• Deno - Next-generation JavaScript Runtime / Native support for TypeScript and JSX
• TS-PICO-8 - TypeScript for PICO-8

Handbook

Classes

• inheritance: extends
• interface: implements
• Parameter properties - let you create and initialize a member in one place. (public, protected, private, readonly)

class Octopus {
  constructor(readonly name: string) {}
}
let dad = new Octopus("Man with the 8 strong legs");
dad.name;

Union Types / Intersection Types / Conditional Types

type-casting

• narrowing type

var vs let vs const

var declarations are accessible anywhere within their containing function, module, namespace, or global scope - all which we’ll go over later on - regardless of the containing block. Some people call this var-scoping or function-scoping. Parameters are also function scoped.

When a variable is declared using let, it uses what some call lexical-scoping or block-scoping. Unlike variables declared with var whose scopes leak out to their containing function, block-scoped variables are not visible outside of their nearest containing block or for-loop.

const declarations are like let declarations but, as their name implies, their value cannot be changed once they are bound.

Array / Tuple

Map or Hash (== Indexed Access Types) / SO

• TypeScript Map
• Map class in TypeScript??
• TypeScript hashmap/dictionary interface

code

Any / Void / Null / Undefined / Unknown / Never