Mastering Lazy Loading in Angular
As Angular applications grow, the size of the JavaScript bundle increases. A large bundle means a slower initial download, parsing, and execution time, leading to a sluggish First Contentful Paint (FCP). **Lazy Loading** is the primary architectural pattern used to combat this.
The Concept: Feature Modules
To implement lazy loading, your application must be structured into **Feature Modules**. You cannot lazy load individual components directly; you lazy load `NgModules` (or Standalone Components in modern Angular).
Instead of importing every module into `AppModule` (which is called "Eager Loading"), you use the Router to reference them via file paths.
Deep Dive: `loadChildren` vs `component`
In your `AppRoutingModule`, the distinction is clear:
Eager Loading (Bad for Scale)
{ path: 'home', component: HomeComponent }Requires `HomeComponent` to be imported at the top of the file, bundling it immediately.
Lazy Loading (Good)
{
path: 'admin',
loadChildren: () => import('./admin/admin.module')
.then(m => m.AdminModule)
}Uses dynamic import. Webpack creates a separate "chunk" file for this code.
Preloading Strategies
Lazy loading solves the startup time, but there is a slight delay when the user clicks the link while the network fetches the chunk. **Preloading** solves this.
By setting `preloadingStrategy: PreloadAllModules` in your router config, Angular will load the main app first, let the user interact, and then silently fetch the lazy chunks in the background.
Pro Tip: Never import a lazy-loaded module into your `AppModule` imports array. If you do, it will be eagerly loaded, defeating the entire purpose of your router configuration.
