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How do you optimize initial bundle size using Route Preloading with custom strategies?

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01

Understand the problem

Explain customizing Route Preloading to selectively load lazy routes.

routingperformance
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03

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Custom preloading strategies implement PreloadingStrategy and its preload() method. By checking custom route.data properties (e.g., { preload: true }), they dynamically decide whether to load lazy route bundles immediately after startup.

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04

Read the code

Implementing a custom preloading strategy based on route data flags
import { Injectable } from '@angular/core';
import { PreloadingStrategy, Route } from '@angular/router';
import { Observable, of } from 'rxjs';

@Injectable({ providedIn: 'root' })
export class CustomPreloadStrategy implements PreloadingStrategy {
  preload(route: Route, fn: () => Observable<any>): Observable<any> {
    const shouldPreload = route.data && route.data['preload'] === true;
    return shouldPreload ? fn() : of(null);
  }
}
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