Introduction to Types in TypeScript

Introduction

TypeScript, an open source language, is a typed superset of JavaScript that compiles to plain JavaScript. It adds optional static typing and class-based object oriented programming to the language. Some of the key features it provides are type support and code encapsulation.

Overview of the relation between TypeScript and JavaScript

 

 

As in the above figure, MathCalculator.ts is a TypeScript file that is compiled by tsc, the TypeScript compiler, to the MathCalculator.js file. Then one can use this MathCalculator.js in their application.

OOPS Features of TypeScript

1. Supports Key JavaScript Features

2. Provides static typing

3. Supports constructors, properties and functions

4. Define Interfaces

5. Encapsulation through classes and modules

6. Support lambdas => 

TypeScript Annotations

  Primitive Types
 

Basic primitive types are number, bool, string, null and undefined.


 

Object Types

Object literals

Functions

Here functions can be used in the following two ways:

1. Assigning the function directly

2. Defining a type as a function and then assign a function

 

 

Arrow function expressions

Equivalent JavaScript code

Dynamic and Static typing

 

TypeScript	JavaScript
Static typing is optional here	Only dynamic typing is supported
Type safety is checked at compile time	Type safety is checked at run time

 

Summary

In this article, we have seen that TypeScript *.ts files are compiled to *.js files by the TypeScript compiler (tsc). Also we have seen annotations and various object types available in TypeScript. In future articles, we will  explore classes, interfaces and modules.