Custom validation using form validator in Angular Datepicker component

27 Apr 20244 minutes to read

The client side validation takes place in the browser to avoid the waiting time to receive the response from sever. It validates the form elements to provide the better feedback messages to correct the every fields before the form submission.

To achieve the client side validation in a DatePicker component by using FormValidator function. It provides an option to customize the feedback error messages to the corresponding fields to take action to resolve the issue.

app.component.ts

import { NgModule } from '@angular/core'
import { FormsModule } from '@angular/forms'
import { BrowserModule } from '@angular/platform-browser'
import { DatePickerModule } from '@syncfusion/ej2-angular-calendars'



import { Component, ViewChild, OnInit } from '@angular/core';
import { DatePickerComponent } from '@syncfusion/ej2-angular-calendars';
import { FormValidator, FormValidatorModel } from '@syncfusion/ej2-inputs';
@Component({
imports: [
        
        DatePickerModule,
        FormsModule
    ],


standalone: true,
    selector: 'app-root',
    template: `<form id="form-element" class="form-vertical">
    <ejs-datepicker #ejDate id='datepicker' placeholder='Enter date' width="275px"(blur)="onFocusOut()" (change)= "onChange($event)"></ejs-datepicker>
    </form>`
})
export class AppComponent implements OnInit {
    @ViewChild('formElement') element: any;
    @ViewChild('ejDate') ejDate?: DatePickerComponent;
    public formObject?: FormValidator;
    ngOnInit() {
        // custom validator function.
        let customFn: (args: {
            [key: string]: string
        }) => boolean = (args: {
            [key: string]: string
        }) => {
            return (((this.ejDate as DatePickerComponent ).value).getFullYear() > 1990 && ((this.ejDate as DatePickerComponent ).value).getFullYear() < 2020);
        };
        let options: FormValidatorModel = {
            rules: {
                'datepicker': {
                    required: [true, "Value is required"]
                }
            },
            customPlacement: (inputElement: HTMLElement, errorElement: HTMLElement) => {
                inputElement.parentElement?.parentElement?.appendChild(errorElement);
            }
        };
        this.formObject = new FormValidator('#form-element', options);
        this.formObject.addRules('datepicker', {
            range: [customFn, "Please select a date between years from 1990 to 2020"]
        });
        this.formObject = new FormValidator('#form-element', options);
    }
    // Form validation takes place when focus() event of DatePicker is triggered.
    public onFocusOut(): void {
        this.formObject?.validate("datepicker");
    }
    // Custom validation takes place when value is changed.
    public onChange(args: any) {
        if (this.ejDate?.value != null)
            this.formObject?.validate("datepicker");
    }
}

main.ts

import { bootstrapApplication } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import 'zone.js';
bootstrapApplication(AppComponent).catch((err) => console.error(err));