TypeScript and Angular: How to use TypeScript with Angular

Are you looking for a way to make your Angular applications more efficient and maintainable? Look no further than TypeScript. TypeScript is a typed superset of JavaScript that makes it easier to write and debug code, while improving code quality and scalability. And when it comes to Angular, using TypeScript can make a world of difference. In this tutorial, we will walk you through the process of using TypeScript with Angular, from installation to best practices.

Prerequisites

Before diving into TypeScript with Angular, make sure you have the following software installed:

• Node.js (version 10.13 or higher)
• Angular CLI (version 8.0.0 or higher)

Installing TypeScript

To use TypeScript with Angular, you need to have TypeScript installed. You can either install it globally or locally to your project. To install globally, run the following command in your terminal:

npm install -g typescript

To install locally to your project, run:

npm install typescript --save-dev

This will add TypeScript to your project's dependencies in the package.json file.

Creating an Angular project with TypeScript

To create a new Angular project with TypeScript, use the Angular CLI. In your terminal, run:

ng new my-project --routing --style=scss

This will create a new Angular project with the specified options. Make sure to replace "my-project" with your project's name.

Once your project is created, open it in your text editor of choice. You will see that there is already a src/app folder with some starter code. Let's explore this code and see where we can integrate TypeScript.

Integrating TypeScript into an Angular project

To integrate TypeScript into your Angular project, you first need to create a TypeScript file. In your src/app folder, create a new file called app.component.ts. This will be our first TypeScript file.

Open app.component.ts in your text editor and add the following code:

import { Component } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.scss']
})
export class AppComponent {
  title = 'My App';
}

This code imports the Component decorator from the @angular/core library and defines a new component called AppComponent. We've also added a title property to the component.

Next, we need to update app.component.html to use our new component. Open app.component.html and replace the default content with the following:

<h1>
  {{ title }}
</h1>

This code displays our title property in an h1 element.

Now that we have our TypeScript code set up, let's compile it and see if it works.

Compiling TypeScript

To compile our TypeScript code, we need to run the tsc command. This command takes a TypeScript file and compiles it into JavaScript.

In your terminal, navigate to your src/app folder and run:

tsc app.component.ts

This will compile the app.component.ts file into a new file called app.component.js.

Next, we need to update our index.html file to include the new JavaScript file. Open index.html and add the following line of code within the body tag:

<script src="app.component.js"></script>

Now we're ready to test our code. Run ng serve in your terminal and navigate to http://localhost:4200. You should see your app title displayed on the page.

Congratulations! You've just integrated TypeScript into your Angular project and written your first TypeScript code.

Type checking with TypeScript

One of the biggest advantages of using TypeScript is its ability to perform type checking. This means that TypeScript will catch errors at compile time instead of run time, and can even suggest fixes to prevent those errors.

Let's explore how to use type checking with Angular.

Type annotations

To use type checking in TypeScript, you first need to use type annotations. Type annotations tell TypeScript what type a variable is.

For example, let's update our title property to include a type annotation. Change the title line in app.component.ts to the following:

title: string = 'My App';

Here, we've added a type annotation of string to our title property. This tells TypeScript that title should be of type string.

If we were to assign a value of a different type to title, TypeScript would throw an error at compile time. This helps catch mistakes early and prevent runtime errors.

Interface

Another powerful feature of TypeScript is interfaces. Interfaces define the shape of an object, including its properties and types.

Let's create an interface for our AppComponent. In app.component.ts, add the following code above the AppComponent class:

interface App {
  title: string;
  description?: string;
}

Here, we've defined an interface called App that has two properties: title, which is required and of type string, and description, which is optional and of type string.

Next, let's update our AppComponent class to implement this interface. Change the line that defines AppComponent to the following:

export class AppComponent implements App {

This tells TypeScript that AppComponent must implement the App interface, which means it must have a title property of type string, and it can optionally have a description property of type string.

If we were to define AppComponent without implementing the App interface, TypeScript would throw an error at compile time, letting us know that our component doesn't match the expected shape.

Class properties and methods

TypeScript also offers support for class properties and methods, which can make working with Angular easier.

For example, let's add a method to our AppComponent class that logs a message to the console when the component is initialized. Add the following code to app.component.ts, below the title property:

constructor() {
  console.log('Component initialized');
}

This code adds a constructor method to our AppComponent class that logs a message to the console. The constructor is a special method that is called when the component is initialized.

By using class properties and methods, we can write more organized and concise code, and take advantage of TypeScript's powerful type checking.

Conclusion

TypeScript offers many benefits when used with Angular, including improved code quality, scalability, and maintainability. By using TypeScript's type checking and interfaces, you can catch errors early and write more robust code. And by taking advantage of TypeScript's class properties and methods, you can write more organized and concise code.

In this tutorial, we've walked through the process of using TypeScript with Angular, from installation to best practices. We hope this tutorial has helped you get started with TypeScript and Angular, and we look forward to seeing what you build with them.

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