Chahdi - Type Script Notes for Professionals: typed superset of JavaScript

TypeScriptDisclaimer This is an unocial free book created for educational purposes and is

not aliated with ocial TypeScript group(s) or company(s). All trademarks and registered trademarks are the property of their respective owners

Chapter 1: Getting started with TypeScript .................................................................................................... 2
Section 1.1: Installation and setup ................................................................................................................................. 2
Section 1.2: Basic syntax ............................................................................................................................................... 4

Chapter 16: Publish TypeScript definition files ............................................................................................ 52

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Version Release Date
2.8.3 2018-04-20
2.8 2018-03-28
2.8 RC 2018-03-16
2.7.2 2018-02-16
2.7.1 2018-02-01
2.7 beta 2018-01-18
2.6.1 2017-11-01
2.5.2 2017-09-01
2.4.1 2017-06-28
2.3.2 2017-04-28
2.3.1 2017-04-25
2.3.0 beta 2017-04-04
2.2.2 2017-03-13
2.2 2017-02-17
2.1.6 2017-02-07
2.2 beta 2017-02-02
2.1.5 2017-01-05
2.1.4 2016-12-05
2.0.8 2016-11-08
2.0.7 2016-11-03
2.0.6 2016-10-23
2.0.5 2016-09-22
2.0 Beta 2016-07-08
1.8.10 2016-04-09
1.8.9 2016-03-16
1.8.5 2016-03-02
1.8.2 2016-02-17
1.7.5 2015-12-14
1.7 2015-11-20
1.6 2015-09-11
1.5.4 2015-07-15
1.5 2015-07-15
1.4 2015-01-13
1.3 2014-10-28
1.1.0.1 2014-09-23

Background

TypeScript is a typed superset of JavaScript that compiles directly to JavaScript code. TypeScript files commonly use the .ts extension. Many IDEs support TypeScript without any other setup required, but TypeScript can also be compiled with the TypeScript Node.JS package from the command line.

IDEs
Visual Studio

Visual Studio 2015 includes TypeScript.
Visual Studio 2013 Update 2 or later includes TypeScript, or you can download TypeScript for earlier versions .

Visual Studio Code
Visual Studio Code (vscode) provides contextual autocomplete as well as refactoring and debugging tools for TypeScript. vscode is itself implemented in TypeScript. Available for Mac OS X, Windows and Linux.
WebStorm
WebStorm 2016.2 comes with TypeScript and a built-in compiler. [WebStorm is not free]
IntelliJ IDEA
IntelliJ IDEA 2016.2 has support for TypeScript and a compiler via a plugin maintained by the JetBrains team. [IntelliJ is not free]
Atom & atom-typescript
Atom supports TypeScript with the atom-typescript package.
Sublime Text
Sublime Text supports TypeScript with the TypeScript package.

Installing the command line interface Install Node.js
Install the npm package globally

You can install TypeScript globally to have access to it from any directory.
npm install -g typescript
or
Install the npm package locally
You can install TypeScript locally and save to package.json to restrict to a directory.
npm install typescript --save-dev Installation channels
You can install from:

Stable channel: npm install typescript Beta channel: npm install typescript@ beta Dev channel: npm install typescript@ next

Compiling TypeScript code
The tsc compilation command comes with typescript, which can be used to compile code.
tsc my- code.ts
This creates a my- code.js file.
Compile using tsconfig.json

You can also provide compilation options that travel with your code via a tsconfig. json file. To start a new TypeScript project, cd into your project's root directory in a terminal window and run tsc - init. This command will generate a tsconfig.json file with minimal configuration options, similar to below.

{ "compilerOptions" : {
"module" : "commonjs" , "target" : "es5" ,
"noImplicitAny" : false , "sourceMap" : false , "pretty" : true

},
"exclude" : [
"node_modules"
]
}
With a tsconfig.json file placed at the root of your TypeScript project, you can use the tsc command to run the compilation. TypeScript is a typed superset of JavaScript, which means that all JavaScript code is valid TypeScript code. TypeScript adds a lot of new features on top of that.

TypeScript makes JavaScript more like a strongly-typed, object-oriented language akin to C# and Java. This means that TypeScript code tends to be easier to use for large projects and that code tends to be easier to understand and maintain. The strong typing also means that the language can (and is) precompiled and that variables cannot be assigned values that are out of their declared range. For instance, when a TypeScript variable is declared as a number, you cannot assign a text value to it.

This strong typing and object orientation makes TypeScript easier to debug and maintain, and those were two of the weakest points of standard JavaScript.
Type declarations

You can add type declarations to variables, function parameters and function return types. The type is written after a colon following the variable name, like this: var num: number = 5 ; The compiler will then check the types (where possible) during compilation and report type errors.

var num: number = 5 ;
num = "this is a string" ; // error: Type 'string' is not assignable to type 'number'.
The basic types are :

number (both integers and floating point numbers)
string
boolean
Array. You can specify the types of an array's elements. There are two equivalent ways to define array types: Array< T> and T[] . For example:

number[] - array of numbers
Array< string> - array of strings

Tuples. Tuples have a fixed number of elements with specific types.
[ boolean , string] - tuple where the first element is a boolean and the second is a string. [ number, number, number] - tuple of three numbers.

{} - object, you can define its properties or indexer
{ name: string, age: number} - object with name and age attributes
{[ key: string]: number} - a dictionary of numbers indexed by string

enum - { Red = 0 , Blue, Green } - enumeration mapped to numbers

Function. You specify types for the parameters and return value:
( param: number) => string - function taking one number parameter returning string () => number - function with no parameters returning an number.
( a: string, b?: boolean ) => void - function taking a string and optionally a boolean with no return value.

any - Permits any type. Expressions involving any are not type checked.
void - represents "nothing", can be used as a function return value. Only null and undefined are part of the void type.
never

let foo: never; -As the type of variables under type guards that are never true.
function error( message: string): never { throw new Error( message); } - As the return type of functions that never return.

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