Custom form validation

1. How do you create a custom validator?
2. How do you validate a form?
3. What is custom validation in angular?
4. How do you validate a form in HTML?
5. What is dirty in angular?
6. What is form validation?
7. What is front end validation?
8. What are the different types of validation?
9. How do you validate your age?
10. What is FormControl angular?
11. What is ngModel in angular?
12. What is touched in angular?

How do you create a custom validator?

Essentially, to pass parameters to a custom validator you need to follow these steps:

1. Create a factory function and pass parameters that will be passed to the custom validator to this function.
2. The return type of the factory function should be ValidatorFn which is part of @angular/forms.

How do you validate a form?

JavaScript - Form Validation

1. Basic Validation − First of all, the form must be checked to make sure all the mandatory fields are filled in. It would require just a loop through each field in the form and check for data.
2. Data Format Validation − Secondly, the data that is entered must be checked for correct form and value.

What is custom validation in angular?

A validator in Angular is a function which returns null if a control is valid or an error object if it's invalid. For model-driven forms we create custom validation functions and pass them into the FormControl constructor.

How do you validate a form in HTML?

The simplest HTML5 validation feature is the required attribute. To make an input mandatory, add this attribute to the element. When this attribute is set, the element matches the :required UI pseudo-class and the form won't submit, displaying an error message on submission when the input is empty.

What is dirty in angular?

ng-dirty: The ng-dirty class tells that the form has been made dirty (modified ) by the user. It returns true if the user has modified the form. Return type: Return Boolean True if the form/input field is modified by the user else it returns False.

What is form validation?

Form validation is a “technical process where a web-form checks if the information provided by a user is correct.” The form will either alert the user that they messed up and need to fix something to proceed, or the form will be validated and the user will be able to continue with their registration process.

What is front end validation?

front-end validation in forms is able to highlight wrong user input and disable the input button. This is useful to give the user some immediate feedback when entering values in the form. ... This is where back-end validation comes into play.

What are the different types of validation?

There are 4 main types of validation:

• Prospective Validation.
• Concurrent Validation.
• Retrospective Validation.
• Revalidation (Periodic and After Change)

How do you validate your age?

1. Date format dd/MM/yyyy validation: The Date of Birth (DOB) will be first validated for dd/MM/yyyy format using Regular Expression (Regex). 2. 18+ Minimum Age validation: The difference between the age entered in the TextBox and the Current Date is minimum 18 years.

What is FormControl angular?

The FormControl is used to create Angular reactive form. Angular uses three fundamental API to create Angular reactive form that are FormControl , FormGroup and FormArray . FormControl: It is a class that is used to get and set values and validation of a form control such as <input> and <select> tag.

What is ngModel in angular?

ngModel is a directive which binds input, select and textarea, and stores the required user value in a variable and we can use that variable whenever we require that value. It also is used during validations in a form. We can use ngModel with: input. text.

What is touched in angular?

In Pro Angular-6 book is detailed as below; valid: This property returns true if the element's contents are valid and false otherwise. ... untouched: This property returns true if the user has not visited the element. touched: This property returns true if the user has visited the element.