How to Build Library for Angular Apps: Everything You Need to Know

Introduction: Why Building Libraries in Angular Is Useful

An Angular library is a central repository of reusable components, ensuring consistent design patterns and standards across multiple projects. It enables efficient teamwork by allowing developers to work simultaneously on different aspects of an application. Developers can summarise commonly used functionalities by developing libraries, share components and services across projects, and simplify the development process. 

This blog explores the advantages of building an Angular library, and the angular material design. You will learn about how it contributes to efficient and scalable application development. 

Getting Started: Setting Up Your Angular Library Project

Follow these steps to set up your Angular library project:

  1. Create a new directory for your library project.
  2. Open a terminal and navigate to the project directory.
  3. Run the command ng new your-library-name to generate a new Angular project.
  4. Change into the project directory using cd your-library-name.
  5. Generate a new library by running ng generate library your-library-name.
  6. The library files will be generated in the projects/your-library-name directory.
  7. Open the library module file (your-library-name.module.ts) and add your components, services, and other code.
  8. Build your library using ng build your-library-name to generate the distributable files.
  9. Your library is ready to be published or used in other Angular projects.

Creating Components: Building Reusable Components for Your Library

Follow the given guidelines to develop reusable components for your Angular library:

  • Generate a new component in your library project using the Angular CLI command: ng generate component component-name –project=your-library-name.
  • The angular material components will be created within the projects/your-library-name/src/lib directory.
  • Modify the component file (component-name.component.ts) to define its behaviour and functionality.
  • Design the component template (component-name.component.html) to structure its layout and elements.
  • Customise the component’s styles by editing the associated CSS file (component-name.component.css).
  • Add the component to the exports array to ensure it is exported in the library’s module file (your-library-name.module.ts).
  • Run ng build your-library-name, incorporating the updated component and compiling the angular component library.
  • Your reusable angular material components are now prepared for utilisation within your library or other Angular projects.

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Services and Pipes: Adding Services and Pipes to Your Library

Services and pipes are fundamental features in Angular, offering reusability and modularity.

Services handle business logic, data manipulation, and communication with external APIs or backend services. To include service in your Angular library,

  • Create a new service file using the Angular CLI command: 

ng generate service service-name –project=your-library-name

  • Define the service’s logic and methods in the generated file and export it from your library’s module file.

Pipes transform data in Angular templates, allowing output modification before displaying it. To add a pipe to your Angular library,

  • Use ng generate pipe pipe-name –project=your-library-name
  • Customise the pipe’s transformation logic in the generated file and export it from your library’s module file.

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Module Configuration: Configuring Your Library’s Module

Module configuration in the context of an Angular library involves customising the module file (your-library-name.module.ts), specifying the library’s functionality and dependencies.

Follow these steps to configure your Angular library’s module:

  • Open the module file (your-library-name.module.ts) in your library project.
  • Use the “import” statement to bring in necessary dependencies, such as Angular modules or third-party libraries.
  • Add your library’s components, services, and pipes to the “declarations” array, making them accessible within the module.
  • Include any external modules or dependencies your library relies on in the “imports” array to use their functionality fully.
  • Place services your library exposes in the “providers” array for dependency injection.
  • Add components, services, or pipes that need to be accessible outside the library to the exports array.
  • By configuring the module of your Angular library, you define dependencies, declare components and services, and ensure smooth integration into Angular applications. Consider joining a Full Stack Software Development Bootcamp to understand software development better. 

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Packaging and Publishing: Preparing Your Library for Distribution

Packaging and publishing involve preparing your Angular library for distribution, enabling others to use it in their projects.

To prepare your Angular library for distribution, follow these steps:

  • Compile your library: Employ the Angular CLI command ng build your-library-name to generate the compiled output, resulting in a dist folder containing the packaged library version.
  • Package your library: Bundle all required files and dependencies into a distributable format using a module bundler like Webpack or Rollup, offering different file formats such as UMD, CommonJS, or ES modules.
  • Create a package.json file: Craft a package.json file in the library’s root directory, including essential information like name, version, description, dependencies, and entry points.
  • Specify entry points: Define the entry points of your library in the package.json file, guiding users on which files to import when using your library.
  • Publish to a package registry: Distribute your library by publishing it to a package registry like npm or a private repository, enabling users to install and employ it via npm install easily.
  • Document your library: Provide comprehensive documentation covering installation instructions, usage examples, and API references to help users integrate and leverage your library effectively.

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Using Your Library: Importing and Using Your Library in Other Angular Projects

Importing and using your library in other Angular projects offers several advantages. It promotes code reusability, allowing you to leverage the functionality and angular material components you have developed in your library across multiple projects. This saves time and effort by avoiding the need to recreate similar features from scratch. Follow these steps to incorporate your Angular library into other projects:

  • Install your library: Use the command npm install your-library-name to install your library as a dependency in the desired Angular project.
  • Import the library: In the component or module where you want to employ your library, import the required modules, components, services, or pipes from your library using the import statement.
  • Add the library to module dependencies: Include your library in the imports array of the Angular module where you intend to use it. This grants access to the library’s functionality within that module.
  • Employ the library components and services: In your project’s components or services, apply the imported library components and services as needed, using their functionality to enhance your project’s features and capabilities.

Testing Your Library: Writing and Running Tests for Your Library

Follow these steps to examine and ensure the quality and reliability of your Angular library:

  • Set up the testing environment: Create a dedicated folder within your library project to house your tests. Configure the necessary testing frameworks and dependencies, such as Karma and Jasmine.
  • Write unit tests: Develop unit tests for your library’s components, services, and other units of functionality. Use the Jasmine testing framework and its suite of testing functions to define test cases and assertions.
  • Write integration tests: Create integration tests to verify that different components or services within your library work together correctly. This helps ensure that the various parts of your library integrate seamlessly.
  • Write end-to-end (E2E) tests: Craft end-to-end tests to simulate user interactions and validate the behaviour of your library within a complete application flow. Use frameworks like Protractor or Cypress for E2E testing.
  • Run the tests: Execute your tests using the appropriate testing command (e.g., ng test for unit tests, ng e2e for end-to-end tests). Monitor the test results to identify any failures or issues.
  • Continuously maintain and update tests: Regularly review and update your tests to align with changes and enhancements made to your library. This ensures that your tests remain effective and reliable over time.

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Best Practices: Tips and Tricks for Building High-Quality Angular Libraries

Here are some tips and tricks to help you build high-quality Angular libraries:

  • Plan and design your Angular library carefully to ensure it meets the specific needs of your target audience.
  • Adhere to established Angular coding conventions and best practices to maintain consistency and facilitate code maintenance.
  • Break down your library’s functionality into modular and reusable components to promote code reusability and easy integration.
  • Handle errors and edge cases gracefully with proper error-handling mechanisms and informative error messages.
  • Stay updated with the latest Angular versions and dependencies to ensure compatibility and leverage new features and improvements.
  • Engage with the Angular community to gather feedback and incorporate valuable insights to enhance your library.
  • Maintain and improve your library regularly, addressing issues, adding new features, and encouraging community contributions for collaborative development.

Wrapping up

Creating a top-notch Angular library necessitates meticulous planning, adherence to best practices, and a strong emphasis on usability and performance. You can develop a dependable and user-friendly library by following established conventions, modularising components, delivering comprehensive documentation, and conducting rigorous testing. 

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What is the most recommended library for Angular?

If you are looking for a reliable Angular component library, here is a list of the top libraries: Angular Material, CoreUI, Clarity Design Systems, Nebular, NG-Bootstrap, Ignite UI, Onsen UI and NG Lightning.

What is the command used to generate a library in an Angular project?

The ng generate command creates a folder named my-lib in your workspace projects directory. This folder includes a NgModule, a component and a service within it.

What is the difference between an Angular library vs module?

An Angular library is a collection of reusable components, services, and assets, while an Angular module is a way to organise and group components and services within an Angular application.

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