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/Angular 7

Validators

class

Provides a set of built-in validators that can be used by form controls.

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class Validators {
  static min(min: number): ValidatorFn
  static max(max: number): ValidatorFn
  static required(control: AbstractControl): ValidationErrors | null
  static requiredTrue(control: AbstractControl): ValidationErrors | null
  static email(control: AbstractControl): ValidationErrors | null
  static minLength(minLength: number): ValidatorFn
  static maxLength(maxLength: number): ValidatorFn
  static pattern(pattern: string | RegExp): ValidatorFn
  static nullValidator(control: AbstractControl): ValidationErrors | null
  static compose(validators: ValidatorFn[]): ValidatorFn | null
  static composeAsync(validators: AsyncValidatorFn[]): AsyncValidatorFn | null
}

See also

Description

A validator is a function that processes a FormControl or collection of controls and returns an error map or null. A null map means that validation has passed.

Static methods

Validator that requires the control's value to be greater than or equal to the provided number. The validator exists only as a function and not as a directive.

static min(min: number): ValidatorFn

Parameters
min number
Returns

ValidatorFn: A validator function that returns an error map with the min property if the validation check fails, otherwise null.

Usage Notes

Validate against a minimum of 3
const control = new FormControl(2, Validators.min(3));

console.log(control.errors); // {min: {min: 3, actual: 2}}

Validator that requires the control's value to be less than or equal to the provided number. The validator exists only as a function and not as a directive.

static max(max: number): ValidatorFn

Parameters
max number
Returns

ValidatorFn: A validator function that returns an error map with the max property if the validation check fails, otherwise null.

Usage Notes

Validate against a maximum of 15
const control = new FormControl(16, Validators.max(15));

console.log(control.errors); // {max: {max: 15, actual: 16}}

Validator that requires the control have a non-empty value.

static required(control: AbstractControl): ValidationErrors | null

Parameters
control AbstractControl
Returns

ValidationErrors | null: An error map with the required property if the validation check fails, otherwise null.

Usage Notes

Validate that the field is non-empty
const control = new FormControl('', Validators.required);

console.log(control.errors); // {required: true}

Validator that requires the control's value be true. This validator is commonly used for required checkboxes.

static requiredTrue(control: AbstractControl): ValidationErrors | null

Parameters
control AbstractControl
Returns

ValidationErrors | null: An error map that contains the required property set to true if the validation check fails, otherwise null.

Usage Notes

Validate that the field value is true
const control = new FormControl('', Validators.requiredTrue);

console.log(control.errors); // {required: true}

Validator that requires the control's value pass an email validation test.

static email(control: AbstractControl): ValidationErrors | null

Parameters
control AbstractControl
Returns

ValidationErrors | null: An error map with the email property if the validation check fails, otherwise null.

Usage Notes

Validate that the field matches a valid email pattern
const control = new FormControl('[email protected]', Validators.email);

console.log(control.errors); // {email: true}

Validator that requires the length of the control's value to be greater than or equal to the provided minimum length. This validator is also provided by default if you use the the HTML5 minlength attribute.

static minLength(minLength: number): ValidatorFn

Parameters
minLength number
Returns

ValidatorFn: A validator function that returns an error map with the minlength if the validation check fails, otherwise null.

Usage Notes

Validate that the field has a minimum of 3 characters
const control = new FormControl('ng', Validators.minLength(3));

console.log(control.errors); // {minlength: {requiredLength: 3, actualLength: 2}}
<input minlength="5">

Validator that requires the length of the control's value to be less than or equal to the provided maximum length. This validator is also provided by default if you use the the HTML5 maxlength attribute.

static maxLength(maxLength: number): ValidatorFn

Parameters
maxLength number
Returns

ValidatorFn: A validator function that returns an error map with the maxlength property if the validation check fails, otherwise null.

Usage Notes

Validate that the field has maximum of 5 characters
const control = new FormControl('Angular', Validators.maxLength(5));

console.log(control.errors); // {maxlength: {requiredLength: 5, actualLength: 7}}
<input maxlength="5">

Validator that requires the control's value to match a regex pattern. This validator is also provided by default if you use the HTML5 pattern attribute.

static pattern(pattern: string | RegExp): ValidatorFn

Parameters
pattern string | RegExp
Returns

ValidatorFn: A validator function that returns an error map with the pattern property if the validation check fails, otherwise null.

Note that if a Regexp is provided, the Regexp is used as is to test the values. On the other hand, if a string is passed, the ^ character is prepended and the $ character is appended to the provided string (if not already present), and the resulting regular expression is used to test the values.

Usage Notes

Validate that the field only contains letters or spaces
const control = new FormControl('1', Validators.pattern('[a-zA-Z ]*'));

console.log(control.errors); // {pattern: {requiredPattern: '^[a-zA-Z ]*$', actualValue: '1'}}
<input pattern="[a-zA-Z ]*">

Validator that performs no operation.

static nullValidator(control: AbstractControl): ValidationErrors | null

Parameters
control AbstractControl
Returns

ValidationErrors | null

Compose multiple validators into a single function that returns the union of the individual error maps for the provided control.

static compose(validators: null): null

Parameters
validators null
Returns

null: A validator function that returns an error map with the merged error maps of the validators if the validation check fails, otherwise null.

static compose(validators: ValidatorFn[]): ValidatorFn | null

Parameters
validators ValidatorFn[]
Returns

ValidatorFn | null

Compose multiple async validators into a single function that returns the union of the individual error objects for the provided control.

static composeAsync(validators: AsyncValidatorFn[]): AsyncValidatorFn | null

Parameters
validators AsyncValidatorFn[]
Returns

AsyncValidatorFn | null: A validator function that returns an error map with the merged error objects of the async validators if the validation check fails, otherwise null.

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Licensed under the Creative Commons Attribution License 4.0.
https://v7.angular.io/api/forms/Validators