How can you create, test, and deploy Angular libraries? — Angular Interview Question #48

Creating, testing, and deploying Angular libraries involve several steps that can be achieved using the Angular CLI, testing tools like Jasmine and Karma, and package managers like npm. Let’s break down these steps in detail:

### 1. Creating Angular libraries

To create an Angular library, follow these steps:

1.1 Install Angular CLI globally if you don’t have it already:

npm install -g @angular/cli

1.2 Create a new Angular workspace:

ng new my-workspace --create-application=false

‘–create-application=false‘ flag indicates that you don’t want to create an initial application within the workspace.

1.3 Navigate to the workspace directory:

cd my-workspace

1.4 Generate a new library in the workspace:

ng generate library my-library

This command will create a set of files under the ‘projects/my-library‘ directory.

1.5 Implement your library features under ‘projects/my-library/src/lib‘ directory and export them using the ‘public-api.ts‘ file.

### 2. Testing Angular libraries

For testing Angular libraries, we use Jasmine and Karma:

2.1 The library generated using the Angular CLI will include Jasmine and Karma configurations by default in ‘karma.conf.js‘ and ‘projects/my-library/src/test.ts‘ files. Make sure to put your test files inside the ‘projects/my-library/src/lib‘ folder and have a ‘.spec.ts‘ suffix.

2.2 To run the tests, execute the following command:

ng test my-library

This command will run the tests and display the results in the terminal.

### 3. Building Angular libraries

3.1 Build the library:

ng build my-library

This will generate the build artifacts in the ‘dist/my-library‘ folder.

3.2 Verify the build by looking into the ‘dist/my-library‘ folder. The output should contain folders such as ‘bundles‘, ‘esm2015‘, ‘fesm2015‘, ‘lib‘, along with the various files like ‘package.json‘, ‘.d.ts‘, and ‘.js‘ files.

### 4. Deploying Angular libraries

4.1 To deploy your library, first, we need to publish it to a package registry like npm. First, navigate to the built folder:

cd dist/my-library

4.2 Configure npm to use your npm account. If you don’t have an account, create one [here.](https://www.npmjs.com/signup) Run the following command to login to npm: “‘bash npm login “‘ Provide your npm username, password, and email when prompted.

4.3 Modify the ‘package.json‘ file to provide information about the library such as name, version, and description. Make sure the ‘name‘ field is unique among the npm packages.

4.4 Publish the library:

npm publish

This will deploy your Angular library to the npm registry. After successful deployment, your library will be accessible and can be installed using:

npm install <your-library-name>

Now you’ve successfully created, tested, and deployed an Angular library. Keep in mind that it’s essential to follow semantic versioning when making updates to your library. Update the version number in your ‘package.json‘ accordingly for each new release.