Angular 2管道:如何按多个字段排序？

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
  name: 'multiSort'
})
export class MultiSortPipe implements PipeTransform {
  transform(array: any[], fields: string[]): any[] {
    if (!Array.isArray(array)) {
      return array;
    }

    return array.sort((a, b) => {
      for (let field of fields) {
        let valueA = this.getPropertyValue(a, field);
        let valueB = this.getPropertyValue(b, field);

        if (valueA < valueB) {
          return -1;
        } else if (valueA > valueB) {
          return 1;
        }
      }

      return 0;
    });
  }

  private getPropertyValue(object: any, field: string): any {
    if (typeof object === 'object' && object !== null && field in object) {
      return object[field];
    }

    return null;
  }
}

<ul>
  <li *ngFor="let item of items | multiSort:['name', 'age']">{{ item.name }} - {{ item.age }}</li>
</ul>