Angular 8中的日期验证器，用于比较两个日期

<input type="date" [(ngModel)]="startDate" name="startDate" required>
<input type="date" [(ngModel)]="endDate" name="endDate" required>

import { Component } from '@angular/core';
import { Validators, FormControl, FormGroup } from '@angular/forms';

@Component({
  selector: 'app-date-comparison',
  templateUrl: './date-comparison.component.html',
  styleUrls: ['./date-comparison.component.css']
})
export class DateComparisonComponent {
  dateForm: FormGroup;

  constructor() {
    this.dateForm = new FormGroup({
      startDate: new FormControl('', Validators.required),
      endDate: new FormControl('', Validators.required)
    }, this.dateComparisonValidator);
  }

  dateComparisonValidator(form: FormGroup): { [key: string]: boolean } | null {
    const startDate = form.get('startDate').value;
    const endDate = form.get('endDate').value;

    if (startDate && endDate && startDate > endDate) {
      return { 'dateComparison': true };
    }

    return null;
  }

  get startDate() { return this.dateForm.get('startDate'); }
  get endDate() { return this.dateForm.get('endDate'); }

  onSubmit() {
    if (this.dateForm.valid) {
      // 日期验证通过，继续处理其他逻辑
    }
  }
}

input.ng-invalid.ng-touched {
  border: 1px solid red;
}