Where X=TypeScript

Get the code: learntypescript.ts

TypeScript is a language that aims at easing development of large scale applications written in JavaScript.TypeScript adds common concepts such as classes, modules, interfaces, generics and (optional) static typing to JavaScript.It is a superset of JavaScript: all JavaScript code is valid TypeScript code so it can be added seamlessly to any project. The TypeScript compiler emits JavaScript.

This article will focus only on TypeScript extra syntax, as opposed toJavaScript.

To test TypeScript’s compiler, head to the Playground where you will be able to type code, have auto completion and directly see the emitted JavaScript.

// There are 3 basic types in TypeScriptvar isDone: boolean = false;var lines: number = 42;var name: string = "Anders";// When it's impossible to know, there is the "Any" typevar notSure: any = 4;notSure = "maybe a string instead";notSure = false; // okay, definitely a boolean// For collections, there are typed arrays and generic arraysvar list: number[] = [1, 2, 3];// Alternatively, using the generic array typevar list: Array<number> = [1, 2, 3];// For enumerations:enum Color {Red, Green, Blue};var c: Color = Color.Green;// Lastly, "void" is used in the special case of a function returning nothingfunction bigHorribleAlert(): void {  alert("I'm a little annoying box!");}// Functions are first class citizens, support the lambda "fat arrow" syntax and// use type inference// The following are equivalent, the same signature will be infered by the// compiler, and same JavaScript will be emittedvar f1 = function(i: number): number { return i * i; }// Return type inferredvar f2 = function(i: number) { return i * i; }var f3 = (i: number): number => { return i * i; }// Return type inferredvar f4 = (i: number) => { return i * i; }// Return type inferred, one-liner means no return keyword neededvar f5 = (i: number) =>  i * i;// Interfaces are structural, anything that has the properties is compliant with// the interfaceinterface Person {  name: string;  // Optional properties, marked with a "?"  age?: number;  // And of course functions  move(): void;}// Object that implements the "Person" interface// Can be treated as a Person since it has the name and move propertiesvar p: Person = { name: "Bobby", move: () => {} };// Objects that have the optional property:var validPerson: Person = { name: "Bobby", age: 42, move: () => {} };// Is not a person because age is not a numbervar invalidPerson: Person = { name: "Bobby", age: true };// Interfaces can also describe a function typeinterface SearchFunc {  (source: string, subString: string): boolean;}// Only the parameters' types are important, names are not important.var mySearch: SearchFunc;mySearch = function(src: string, sub: string) {  return src.search(sub) != -1;}// Classes - members are public by defaultclass Point {  // Properties    x: number;    // Constructor - the public/private keywords in this context will generate    // the boiler plate code for the property and the initialization in the    // constructor.    // In this example, "y" will be defined just like "x" is, but with less code    // Default values are also supported    constructor(x: number, public y: number = 0) {        this.x = x;    }    // Functions    dist() { return Math.sqrt(this.x * this.x + this.y * this.y); }    // Static members    static origin = new Point(0, 0);}var p1 = new Point(10 ,20);var p2 = new Point(25); //y will be 0// Inheritanceclass Point3D extends Point {    constructor(x: number, y: number, public z: number = 0) {        super(x, y); // Explicit call to the super class constructor is mandatory    }    // Overwrite    dist() {        var d = super.dist();        return Math.sqrt(d * d + this.z * this.z);    }}// Modules, "." can be used as separator for sub modulesmodule Geometry {  export class Square {    constructor(public sideLength: number = 0) {    }    area() {      return Math.pow(this.sideLength, 2);    }  }}var s1 = new Geometry.Square(5);// Local alias for referencing a moduleimport G = Geometry;var s2 = new G.Square(10);// Generics// Classesclass Tuple<T1, T2> {    constructor(public item1: T1, public item2: T2) {    }}// Interfacesinterface Pair<T> {    item1: T;    item2: T;}// And functionsvar pairToTuple = function<T>(p: Pair<T>) {    return new Tuple(p.item1, p.item2);};var tuple = pairToTuple({ item1:"hello", item2:"world"});// Including references to a definition file:/// <reference path="jquery.d.ts" />

Further Reading

• TypeScript Official website
• TypeScript language specifications (pdf)
• Anders Hejlsberg - Introducing TypeScript on Channel 9
• Source Code on GitHub
• Definitely Typed - repository for type definitions  
  

From:http://learnxinyminutes.com/docs/typescript/