如何根据url的结果更改angular 7网站上的css元素？

<div [ngClass]="{'result-a': isResultA, 'result-b': isResultB}">Content</div>

import { ActivatedRoute } from '@angular/router';

@Component({...})
export class YourComponent {
  isResultA: boolean;
  isResultB: boolean;

  constructor(private route: ActivatedRoute) {
    this.route.queryParams.subscribe(params => {
      const result = params['result'];
      if (result === 'a') {
        this.isResultA = true;
        this.isResultB = false;
      } else if (result === 'b') {
        this.isResultA = false;
        this.isResultB = true;
      }
    });
  }
}

.result-a {
  background-color: red;
}

.result-b {
  background-color: blue;
}