预加载的场景
- 当应用启动后,后续功能可能会被使用到,因此在用户可以使用基础的功能后,再去加载可能使用到的模块
- 只预加载必要的模块,可以提高首次访问网站的速度
代码实现
1 全部预加载
src\app\router\app-routing.module.ts
import { PreloadAllModules, RouterModule } from '@angular/router';
@NgModule({
imports: [
CommonModule,
RouterModule.forRoot(mainRoutes, {
// 预加载全部
preloadingStrategy: PreloadAllModules
})
],
})
2 自定义预加载
自定义路由策略,此处的策略是是路由中携带该参数data: { preload: true}
时预加载该模块
命令
ng g s services/preloadingStrategy
src\app\services\preloading-strategy.service.ts
import { Injectable } from '@angular/core';
import { PreloadingStrategy, Route } from '@angular/router';
import { Observable, of } from 'rxjs';
/**
* 预加载策略
*
* @export
* @class PreloadingStrategyService
* @implements {PreloadingStrategy}
*/
@Injectable({ providedIn: 'root' })
export class PreloadingStrategyService implements PreloadingStrategy {
// 需要预加载的模块
preloadedModules: string[] = [];
preload(route: Route, load: () => Observable<any>): Observable<any> {
if (route.data && route.data['preload']) {
this.preloadedModules.push(route.path as string);
return load();
} else {
return of(null);
}
}
}
如下,在访问时会预先加载welcome2模块
src\app\router\app-routing.module.ts
export const mainRoutes: Routes = [
{
path: 'home',
loadChildren: () => import('../../pages/welcome2/welcome2.module').then((x) => x.Welcome2Module),
data: { preload: true}
},
]
@NgModule({
declarations: [],
imports: [
CommonModule,
RouterModule.forRoot(mainRoutes, {
// 自定义预加载
preloadingStrategy: PreloadingStrategyService
})
],
exports: [
RouterModule
],
providers: [ PreloadingStrategyService ]
})