component.ts

import { Component, AfterViewInit, ViewChild } from '@angular/core';

@Component({
  selector: 'app-modal-demo-show',
  template `
    <ng-template nzbModal #exampleModal="nzbModal">
      <div class="modal fade" tabindex="-1">
        <div class="modal-dialog" role="document">
          <div class="modal-content">
            <div class="modal-header">
              <h5 class="modal-title">Modal Shown On Route Change</h5>
              <button type="button" class="close" data-dismiss="modal" aria-label="Close">
                <span aria-hidden="true">&times;</span>
              </button>
            </div>
            <div class="modal-body">
              <p>
                <a routerLink="/modals">Back to modals</a>
              </p>
            </div>
            <div class="modal-footer">
              <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
            </div>
          </div>
        </div>
      </div>
    </ng-template>
  `
})
export class ModalDemoShowComponent implements AfterViewInit {
  @ViewChild('exampleModal') exampleModal;
  constructor() { }

  ngAfterViewInit() {
    setTimeout(() => {
      this.exampleModal.show();
    })
  }

}