angular4 使用js

// 创建一个共享服务
import { Injectable } from '@angular/core';
import { Subject } from 'rxjs';

@Injectable({
  providedIn: 'root'
})
export class DataService {
  private messageSource = new Subject<string>();
  currentMessage$ = this.messageSource.asObservable();

  changeMessage(message: string) {
    this.messageSource.next(message);
  }
}

// 在组件中使用服务
import { Component } from '@angular/core';
import { DataService } from './data.service';

@Component({
  selector: 'app-sender',
  template: `<button (click)="sendMessage()">Send Message</button>`
})
export class SenderComponent {
  constructor(private dataService: DataService) {}

  sendMessage() {
    this.dataService.changeMessage('Hello from SenderComponent');
  }
}

@Component({
  selector: 'app-receiver',
  template: `{{ message }}`
})
export class ReceiverComponent implements OnInit {
  message: string;

  constructor(private dataService: DataService) {}

  ngOnInit() {
    this.dataService.currentMessage$.subscribe(message => this.message = message);
  }
}

@Component({
  selector: 'app-list',
  template: `
    <ul>
      <li *ngFor="let item of items; trackBy: trackByFn">{{ item.name }}</li>
    </ul>
  `,
  changeDetection: ChangeDetectionStrategy.OnPush
})
export class ListComponent {
  items = [...]; // 假设这是一个大数组

  trackByFn(index, item) {
    return item.id; // 基于唯一标识进行跟踪
  }
}