TypeScript
Concept
TypeScript is a typed superset of JavaScript that compiles to plain JavaScript. TypeScript wird während des Entwicklungsvorgangs mit Hilfe eines Transpilers (eine Sonderform eines Compilers) in JavaScript übersetzt.
Language
Type Annotations
funcXYZ : <RETURN_TYPE> {
}
varXYZ : <TYPE> = ...;
Classes
- constructor short cut: if access modifiers are used no need to declare properties
export class Menu {
constructor(
public id: number,
public parent_id: number,
public name: string,
public comment: string
) {
Interfaces
Typescript uses in interface in multiple ways (s. here:
... implements <INTERFACE_NAME> ...
Access Modifier
- private
- protected
- public
Generics
Decorators
A Decorator is a special kind of declaration that can be attached to a class declaration, method, accessor, property, or parameter. Decorators use the form @<Expression>, where <Expression> must evaluate to a function that will be called at runtime with information about the decorated declaration.
Non-null assertion operator
When you add an exclamation mark after variable/property name, you're telling to TypeScript that you're certain that value is not null or undefined, which prevents the ts2564 compilation error.
Import/Export
Starting with ECMAScript 2015, JavaScript has a concept of modules. TypeScript shares this concept. Each ts-file is javascript module.
import { ZipCodeValidator } from "./ZipCodeValidator"; // import a single export from a module
Installation
C:\Uwes\Programme\nodejs>npm install -g typescript