JavaScript ES6中的静态方法和Angular 2服务

javascript
class MathUtils {
  static add(num1, num2) {
    return num1 + num2;
  }
  static subtract(num1, num2) {
    return num1 - num2;
  }
}
console.log(MathUtils.add(5, 3)); // 输出: 8
console.log(MathUtils.subtract(5, 3)); // 输出: 2

javascript
import { Injectable } from '@angular/core';
@Injectable()
export class DataService {
  private data: string[] = [];
  addData(item: string) {
    this.data.push(item);
  }
  getData() {
    return this.data;
  }
}

javascript
import { Component } from '@angular/core';
import { DataService } from './data.service';
@Component({
  selector: 'app-root',
  template: `
    
Data List
    
      
{{ item }}
    
    Add Item
  `,
  providers: [DataService]
})
export class AppComponent {
  data: string[] = [];
  constructor(private dataService: DataService) {}
  ngOnInit() {
    this.data = this.dataService.getData();
  }
  addItem() {
    this.dataService.addData('New Item');
    this.data = this.dataService.getData();
  }
}