What is TypeScript?

“TypeScript is a typed superset of JavaScript that compiles plain JavaScript”.
We can download this from the official Website.

Key Features of TypeScript

TypeScript to JavaScript

TypeScript compiler (TSC) will convert your TypeScript code into a JavaScript code.
TypeScript
There are different types of examples in the Playground options, which we can choose from the dropdown list.
TypeScript

TypeScript Playground

On this URL, we have the option to write typescript code and you can see the same JavaScript code on the right-hand side.

Basic Data Types in TypeScript

TypeScript supports the following basic data types.
The code represents the basic data type declaration and syntax in Typescript.
  1. let isAuthor: boolean = true
  2. let ArticleCount: number = 100
  3. let AuthorNmae: string = "Shiju"
  4. let ArrayList: number[] = [100, 101.102]
  5. let GenericArrayList: Array < number >= [10, 20, 30]
  6. The“
  7. let” keyword is using instead of “
  8. var” keyword
ts

Tuples and Enums in TypeScript

Tuple types allows you to represent a value as a pair of a string and a number or any other combination.
Here is an example of using the tuples and enums in TypeScript.
  1. let articles: [string, number]
  2. articles = ["shiju", 10]
  3. enum Technologies {
  4. SharePoint,
  5. SQL,
  6. ASP
  7. }
  8. let Tech: Technologies = Technologies.ASP
  9. enum TechnologiesUsed {
  10. SharePoint = 1, SQL = 2, ASP = 3
  11. }
  12. let Techs: TechnologiesUsed = TechnologiesUsed.SharePoint
data types
Examples for "any" are as follows.
  1. “
  2. any” is a dynamic data type.once you declare a variable as any type, you can assign any type of data into that variable
  3. let dynamicdataType: any
  4. dynamicdataType = true;
  5. dynamicdataType = "shiju";
  6. dynamicdataType = 100;
data types

Using void, undefined, and null.

An example of a function with string return type is as follows.
  1. function ArticleNotification(): string {
  2. let message: string = "This is my New article";
  3. return message;
  4. }
  5. function ArticleNotification(): void {
  6. alert("This is my New article");
  7. }
data types

Create a class in TypeScript

  1. class Author {
  2. public AuthorName: string = "Shiju";
  3. }
  4. let authordetails = new Author();
  5. let authorName: string = authordetails.AuthorName
data types

Access modifiers in TypeScript

TypeScript supports the following access modifiers.

Properties in TypeScript

Similar to any other class, TypeScript supports properties. The following is an example of an Author class that has a property, AuthorName.
  1. class Author {
  2. private _AuthorName: string;
  3. public set AuthorName(value: string) {
  4. this._AuthorName = value;
  5. }
  6. public get AuthorName(): string {
  7. return this._AuthorName;
  8. }
  9. }
data types

Methods in TypeScript

The following is an example of a method of a TypeScript class.
  1. class Author {
  2. public AuthorName: string;
  3. isActiveAthour(authorId: number): boolean {
  4. return true;
  5. }
  6. }
data types

Inheritance in TypeScript

To inherit the class in TypeScript, use the “extends” keyword. See the example, mentioned below.
  1. class Author {
  2. public AuthorName: string;
  3. isActiveAthour(authorId: number): boolean {
  4. return true;
  5. }
  6. inheritExample(): void {
  7. alert("Inheritance1")
  8. }
  9. }
  10. class inheritanceOfClass extends Author {
  11. inheritExample(): void {
  12. alert("Inheritance example 2")
  13. }
  14. }
data types

Interface in TypeScript

Use the keyword “implements” for the interface implementation in TypeScript.
  1. interface ITopAuthor {
  2. GetTopAuthor()
  3. }
  4. class Author implements ITopAuthor {
  5. public AuthorName: string = "";
  6. GetTopAuthor() {}
  7. }
data types

Constructor of a class

The example, mentioned below indicates how to create a constructor of a class in TypeScript.
  1. class Author {
  2. public AuthorName: string;
  3. constructor(name: string) {
  4. this.AuthorName = name;
  5. }
  6. }
  7. let authorName = new Author("shiju");
data types
npm Install
 Download the file and install, Open Node.js command prompt.
data types
Execute the command “npm install”.
For more details, refer.
Install TypeScript for Visual Studio
 Download the install file here. Please download the appropriate EXE for the Visual Studio version. Click the EXE file.
data types
data types
Now, the installation is complete.
data types

Create a TypeScript Project

Create a new project in Visual Studio.
data types
Select the Empty Project.
data types
Add a new TypeScript file.
data types
Click Yes here.
data types
Now, we have created the typescript file. In this file, create a class “Author”.
data types
Add a new HTML page to our project.
data types
Add the script, mentioned below on the HTML page.
data types
Run the Application.
data types

Import and Export Modules in TypeScript

JavaScript has a concept of modules that we can do with TypeScript. Import and export are used for this purpose.
The variables, class, functions, interfaces are declared in one module, but they are not available the outside of that module without exporting them, i.e., using the export keyword. Once it's exported, it must be imported, using the import keyword and then these are available in the imported module.
Let's see an example, how we can export and import from different classes.
Add a new Typescript file called Company, which is using the export keyword.
data types
Import our new Company class into our existing Author class. Add export keyword to the Author class.
data types
Add new system.js reference in the HTML page (This is one type of on-demand module loader and I will explain this in my next article), Add the script, mentioned below.
data types
Run the Application.
data types

Conclusion

In this article, we learned basic steps of how to install TypeScript, create a TypeScript app, create classes and their members, and how to import and export class functionality.