What is Tree Shaking In Angular?


Tree shaking is a crucial optimization technique used in modern web development, including in Angular projects. It's a process that removes unused code from your final bundle, making the application lighter and faster to load. Here's how it works specifically in the context of Angular:

1. What is Tree Shaking?

Tree shaking is a step in the build process that involves eliminating dead code — code that is never used or executed. The term comes from the metaphor of shaking a tree to drop the dead leaves (unused code).

2. How Tree Shaking Works in Angular?

Angular applications are built using modules and components, among other elements. Not all of these are always used in the final application. Angular, combined with its build tools (like the Angular CLI), identifies and eliminates the unused parts to reduce the size of the application.

  • Build Process: Angular uses Webpack (through the Angular CLI) to manage the build process, which includes tree shaking. When you build your application for production (using ng build --prod), Angular performs Ahead-of-Time (AOT) compilation, which compiles your Angular HTML and TypeScript code into efficient JavaScript code before the browser downloads and runs it. During this process, the Angular CLI also uses tree shaking to remove unused code.

  • AOT Compilation: AOT plays a significant role in tree shaking because it converts Angular components and templates into JavaScript code ahead of time, allowing Webpack to analyze and shake off unused code more effectively.

3. Benefits of Tree Shaking

  • Reduced Bundle Size: The primary benefit is the reduced size of the final bundle, which means faster download and startup times for your application.
  • Improved Performance: Less JavaScript to parse and execute translates to better performance and quicker interactivity.
  • Cost Efficiency: For mobile users, downloading smaller files can mean less data consumption, which can be crucial in regions with expensive or limited data plans.

4. How to Ensure Effective Tree Shaking?

  • Use ES6 Modules: Make sure you are using ES6 modules, as they are statically analyzable, which is essential for tree shaking to work effectively.
  • Avoid Side Effects in Module Imports: Code that causes side effects when imported can prevent tree shaking. Ensure your code is side-effect free unless necessary.
  • Marking Side Effect-Free Packages in package.json: For library authors, you can help consumers of your library by marking it as side effect-free in its package.json using the "sideEffects": false property, if applicable.
  • Leverage the Angular CLI: The Angular CLI's production build (ng build --prod) automatically applies tree shaking, so make sure to use it for your production builds.

5. Limitations and Considerations

While tree shaking is powerful, it has its limitations. For instance, it might not always catch every unused piece of code, especially if the code has complex side effects that are hard for the build tools to analyze safely.

Tree shaking represents a balance between the complexity of your codebase and the performance gains it can provide. Always test your application thoroughly after a production build to ensure that tree shaking has not inadvertently removed code that you intended to use.

Happy Learning:)

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