Introduction
Angular is one of the most popular frameworks for developing web applications. It has evolved with time and has become more developer-friendly in many ways. One such area of development that Angular has improved over the years is form validation. Angular Reactive Forms validation is a crucial feature that helps developers to ensure that data entered by a user is correct.
In this article, you will learn about Angular Reactive Forms validation and how it ensures that user inputs are correct. It will cover how to write custom validators in Angular, how to use built-in validators, and other necessary information. Lastly, this article will also include an FAQ section to answer some frequently asked questions on Angular Reactive Forms validation.
Angular Reactive Forms
Before diving into Angular Reactive Forms validation, it is important to know what Angular Reactive Forms are. Basically, it is a technique that allows developers to create and manage forms within the Angular framework. Reactive Forms are more flexible and reusable than Template-Driven Forms.
Angular Reactive Forms Validation
Angular Reactive Forms validation allows developers to make sure that the data entered by a user into a form matches the requirements specified for each field. Reactive Forms validation helps developers to detect possible errors promptly and show appropriate feedback to end-users.
There are two types of validators in Angular Reactive Forms: built-in validators and custom validators.
Built-in Validators
Angular provides several built-in validators that can be used to validate form inputs. The following are some of the built-in validators available in Angular:
1. required Validator
The required validator gives an error message if the user does not fill out the form input field. This validator is used to indicate that a user must enter a value.
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2. min and max Validators
The min and max validators ensure that a number falls within the specified range.
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3. email Validator
The email validator ensures that the input data matches a valid email address format.
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Custom Validators
Angular Reactive Forms also allow developers to create custom validators to validate user input. Custom validators can be used to validate data that does not match any of the built-in validators. Writing a custom validator is straightforward, and it will help developers to create their own custom rules to validate a specific form input.
“` html
function validateEmailFormat(control: FormControl) {
const emailRegex = /\S+@\S+\.\S+/;
const isValid = emailRegex.test(control.value);
return isValid ? null : { emailFormat: true };
}
this.myForm = this.formBuilder.group({
email: [”, [Validators.required, validateEmailFormat]],
});
“`
In the above code snippet, a custom validator function `validateEmailFormat` is created that checks whether the email input value matches the email address format.
FAQs on Angular Reactive Forms Validation
1. What are Angular Reactive Forms?
Angular Reactive Forms help developers create and manage forms in the Angular framework. Reactive Forms are more reusable and flexible than Template-Driven Forms.
2. What is Angular Reactive Forms validation?
Angular Reactive Forms validation allows developers to validate user input data and show appropriate feedback to users when data entry errors occur.
3. Which validators are available in Angular Reactive Forms?
Angular Reactive Forms have two types of validators, built-in validators, and custom validators. Some of the built-in validators available in Angular are required, min, max, and email.
4. How do I create a custom validator in Angular Reactive Forms?
A custom validator can be created by defining a function that returns either null or an error object. This function should be added to the array of validators of the specific form input field.
Conclusion
Angular Reactive Forms validation is a crucial feature that helps developers ensure that user inputs are correct. The ability to create custom validators in Angular Reactive Forms is a flexible approach that allows developers to create their own custom rules to validate a specific form input. In conclusion, Angular Reactive Forms validation provides a more powerful toolset for forms validation and is highly recommended for complex forms.