Getting started with

TypeScript

Marcell Kiss

Introduction

Marcell Kiss

JavaScript Development

martzellk

marcellkiss@budacode.com

We'll cover

1. Static vs dynamic typing

2. Compile-to-js languages

3. TypeScript in general

4. TypeScript in practice

5. Conclusion

Static ​​​​

vs 

Dynamic ​​typing​​

Static ​​​​vs dynamic typing

Eric Elliott, @ _ericelliott 

Static types are overrated

Static ​​​​vs dynamic typing

Rafael Ordog, @ devillsroom

Dynamic vs. Static types

source: c0de-x.com

Static ​​​​vs dynamic typing

Dougles Crockford

Microsoft’s TypeScript may be the best of the many JavaScript front ends.

...

...these can be provided nicely by a preprocessor, so there is no need to change the underlying language.

​
I think that JavaScript’s loose typing is one of its best features and that type checking is way overrated. TypeScript adds sweetness, but at a price. It is not a price I am willing to pay.

Static ​​​​vs dynamic typing

Pros and cons written down

Pros:​​

• Reveals bugs in an early stage
• Maintainable

Cons:​​​

• Not so productive
• ​Overrated

Static ​​​​vs dynamic typing

Let's make a survey!

I'll ask two yes/no questions

​Please answer, just if you answer for both.

Compile-to-js languages

What do we have?

Compile-to-js languages

• Dart
• AtScript
• ​CoffeScript
• ​TypeScript

Note: there are hundreds of other solutions...​
https://github.com/jashkenas/coffeescript/wiki/List-of-languages-that-compile-to-JS

Compile-to-js languages

Good old standards...

Compile-to-js languages

Check the trends...

25.01.2016

TypeScript in general

TypeScript in general

'TypeScript lets you write JavaScript the way you really want to.
TypeScript is a typed superset of JavaScript that compiles to plain JavaScript.
Any browser. Any host. Any OS. Open Source.'

 - typescriptlang.org

TypeScript in general

Background

• Microsoft
  TS: 2012 - Present
  Anders Hejlsberg, lead architect of C# and creator of Delphi and Turbo Pascal, has worked on the development of TypeScript.
   
• Angular2
  Changed AtScript to TypeScript
   
• ES7 Proposal: typed objects

TypeScript in general

TypeScript in general

Benefits

'The JavaScript community consolidates tools and frameworks about as often as Nicholas Cage makes a good movie.'

@tjvantoll

• Static analysis
• Opt-in
• ES Compatibility
• Tooling

TypeScript

in practice

TypeScript in practice

Really quick start!

typescriptlang.org/Playground

TypeScript in practice

Basics

// There are 3 basic types in TypeScript
var isDone: boolean = false;
var lines: number = 42;
var name: string = "Anders";

// When it's impossible to know, there is the "Any" type
var notSure: any = 4;
notSure = "maybe a string instead";
notSure = false; // okay, definitely a boolean

// For collections, there are typed arrays and generic arrays
var list: number[] = [1, 2, 3];
// Alternatively, using the generic array type
var 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 nothing
function bigHorribleAlert(): void {
  alert("I'm a little annoying box!");
}

// Sources: learnxinyminutes.com

TypeScript in practice

// Interfaces are structural, anything that has the properties is compliant with
// the interface
interface 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 properties
var 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 number
var invalidPerson: Person = { name: "Bobby", age: true };

// Interfaces can also describe a function type
interface 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;
}

TypeScript in practice

// Classes - members are public by default
class 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

TypeScript in practice

// Inheritance
class 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);
  }
}

TypeScript in practice

// Generics
// Classes
class Tuple<T1, T2> {
  constructor(public item1: T1, public item2: T2) {
  }
}

// Interfaces
interface Pair<T> {
  item1: T;
  item2: T;
}

// And functions
var pairToTuple = function<T>(p: Pair<T>) {
  return new Tuple(p.item1, p.item2);
};

var tuple = pairToTuple({ item1:"hello", item2:"world"});

Get started in local env

// Install using npm
npm install -g typescript

// Compile ts to js
tsc type.ts

// Compile more files into one and set a watcher
tsc *.ts --out app.js --watch

Adding it to your build process using

(grunt / gulp / webpack) is easy

Tooling

Tslint (npm) 

A linter for the TypeScript language.

Typings (npm)

/// <reference path="jquery.d.ts" />

The type definition manager for TypeScript.

Conclusion

Matured technology

'JavaScript safe'

Opt-in

Thanks

for your attention!

Q & A

Sources

Original source - https://github.com/Microsoft/TypeScript
Tutorial - http://www.typescriptlang.org/Tutorial
Samples - http://www.typescriptlang.org/Samples
Handbook - http://www.typescriptlang.org/Handbook
Eric Elliott, Static types are overrated - https://www.youtube.com/watch?v=_kXiH1Yiemw
Ordog Rafael, Static vs dynamic typing - https://www.youtube.com/watch?v=K1D3IQ_L_2Q
The Rise of TypeScript? - http://developer.telerik.com/featured/the-rise-of-typescript/
Comparing to ES6 - http://kangax.github.io/compat-table/es6/ 
Compile to JS - https://github.com/jashkenas/coffeescript/wiki/List-of-languages-that-compile-to-JS
ES7 Proposal: typed objects - https://github.com/hemanth/es7-features
Great place to learn - http://learnxinyminutes.com

TSD - http://definitelytyped.org/tsd/