How To Use Custom Form Validation in Angular

How To Use Custom Form Validation in Angular

Learn how to create a custom validator in Angular for both template-driven and reactive forms. In this tutorial, you will construct a custom validator for a phone number input field in an Angular application.

Learn how to create a custom validator in Angular for both template-driven and reactive forms.

Validators are used to ensure that the values in a form meet certain requirements. They are available to Template-Driven Forms or Reactive Forms in Angular applications.

There are several built-in validators like required, email, pattern, and minLength. It is also possible to develop custom validators to address functionality that is not handled by a built-in validator.

For example, a phone number validator would consist of an input field and will not be considered valid unless the value is ten digits long.

Here is a screenshot of a phone number input field that is providing an invalid number that is nine digits long:

Screenshot of an input field with an invalid phone number. The input is highlighted in a red border and there is an error message indicating the field expects phone number values to be 10 digits long.

And here is a screenshot of a phone number input field that is providing a valid number that is ten digits long:

Screenshot: of an input field with a valid phone number. The input is highlighted with a blue border and there is no error message.

In this tutorial, you will construct a custom validator for a phone number input field in an Angular application.

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