What is JIT and AOT write process in Angular with example

Just-In-Time (JIT) Compilation

Process:

1. Development Phase: JIT compilation happens in the browser at runtime, which means Angular's compiler is included in the application bundle. When you run the Angular application, the Angular compiler translates the application's TypeScript and HTML into JavaScript in the browser just before the application starts.
2. Advantages:
   • Faster build times during development because the application is compiled on the fly.
   • Easier debugging since the source maps are available.
3. Disadvantages:
   • Slower application startup time since the compilation happens in the browser.
   • Larger bundle size due to the inclusion of the Angular compiler.

Example: Running ng serve in development mode uses JIT compilation. The Angular CLI compiles the application as it is served to the browser, allowing developers to see changes instantly without waiting for a complete build process.

Ahead-Of-Time (AOT) Compilation

Process:

1. Build Phase: AOT compilation occurs at build time before the application is served to the browser. The Angular compiler translates TypeScript and HTML into optimized JavaScript code during the build process, resulting in a precompiled bundle.
2. Advantages:
   • Faster application startup time since the compilation has already been done.
   • Smaller bundle size because the Angular compiler is not included in the application bundle.
   • Fewer runtime errors since templates and components are precompiled and validated during the build process.
3. Disadvantages:
   • Longer build times during development.
   • More challenging to debug due to less detailed error messages.

Example: Running ng build --prod in production mode uses AOT compilation. The Angular CLI precompiles the application into optimized JavaScript, which results in a smaller and faster application when deployed.

Summary

• JIT Compilation: Good for development due to faster rebuilds and easier debugging. Used by default when running ng serve.
• AOT Compilation: Ideal for production builds as it produces optimized, smaller bundles and results in faster startup times. Used by default when running ng build --prod.

In essence, JIT is useful during development for its speed and ease of use, while AOT is more suited for production due to its performance benefits and optimized output.