This work is based on Ultimate Angular's ngx-errors.

Overview

Why use ngx-errors, how to install and use.

What is it?

Declarative validation error messages for reactive forms.

Typically you'd do something like this:

<!-- without ngxErrors -->
<input type="text" formControlName="foo" />

<div *ngIf="form.get('foo').hasError('required') && form.get('foo').touched">
  Field is required
</div>
<div *ngIf="form.get('foo').hasError('minlength') && form.get('foo').dirty">
  Min length is 5
</div>

With ngxErrors, we've taken a simple declarative approach that cleans up your templates to make validation easier:

<!-- with ngxErrors -->
<input type="text" formControlName="foo" />

<div ngxErrors="foo">
  <div ngxError="required" when="touched">
    Field is required
  </div>
  <div ngxError="minlength" when="dirty">
    Min length is 5
  </div>
</div>

Check out the documentation below for all the syntax we provide.

Installation

yarn add @kurtz1993/ngx-errors

# OR

npm i @kurtz1993/ngx-errors

Setup

Just add ngx-errors to your module:

import { NgxErrorsModule } from '@kurtz1993/ngx-errors';

@NgModule({ imports: [ NgxErrorsModule ] })

Documentation

ngxErrors

The ngxErrors directive works by dynamically fetching your FormControl under-the-hood, so simply take your formControlName value and pass it into ngxErrors:

<input type="text" formControlName="username" />
<div ngxErrors="username">
  <!-- ... -->
</div>

This needs to be on a parent container that will encapsulate child ngxError directives.

ngxError

The ngxError directive takes either a string or array as arguments. The argument you pass in corresponds to any active errors exposed on your control, such as "required" or "minlength":

<input type="text" formControlName="username" />
<div ngxErrors="username">
  <div ngxError="minlength">
    Min length is 5
  </div>
</div>

Note: when using array syntax, [] bindings are needed

Using the array syntax, when any condition in the array is true the error will be shown:

<input type="text" formControlName="username" />
<div ngxErrors="username">
  <div [ngxError]="['minlength', 'maxlength']">
    Min length is 5, max length is 10
  </div>
</div>

ngxError #when

The when directive takes either a string or array as arguments. It allows you to specify when you wish to display the error based on the control state, such as "dirty" or "touched":

<input type="text" formControlName="username" />
<div ngxErrors="username">
  <div ngxError="minlength" when="dirty">
    Min length is 5
  </div>
</div>

It also comes in array format for multiple rules:

<input type="text" formControlName="username" />
<div ngxErrors="username">
  <div ngxError="minlength" [when]="['dirty', 'touched']">
    Min length is 5
  </div>
</div>

Dynamic errors

You can optionally data-bind and dynamically create validation errors with ngxErrors:

<input type="text" formControlName="username" />
<div ngxErrors="person.username">
  <div *ngFor="let error of errors" [ngxError]="error.name" [when]="error.rules">
    {{ error.text }}
  </div>
</div>

With corresponding component class:

@Component({...})
export class MyComponent {
  errors = [
    { name: 'required', text: 'This field is required', rules: ['touched', 'dirty'] },
    { name: 'minlength', text: 'Min length is 5', rules: ['dirty'] }
  ];
}

Nested FormGroup support

ngxErrors also supports FormGroups with control names using dot notation:

<div formGroupName="person">
  <input type="text" formControlName="username" />
  <div ngxErrors="person.username">
    <div ngxError="minlength" [when]="['dirty', 'touched']">
      Min length is 5
    </div>
  </div>
</div>

Exported Directive API

ngx-errors exports itself as ngxErrors, which means you can access information about your control error states elsewhere in your template using a template reference, such as #foo.

Basic usage:

<div ngxErrors="username" #myError="ngxErrors"></div>

getError(name: string): any;

The getError method returns the object associated with your error. This can be useful for dynamically displaying error rules.

Example: Adds Min length is 5 when value is less than 5 characters (based on Validators.minLength(5)).

<input type="text" formControlName="username" />

<div ngxErrors="username" #myError="ngxErrors">
  <div ngxError="minlength" when="dirty">
    Min length should be {{ myError.getError('minlength')?.requiredLength }}
  </div>
</div>

The error returned is identical to Angular's FormControl API

hasError(name: string, conditions?: string | string[]): boolean;

The hasError method informs you if your control has the given error. This can be useful for styling elsewhere in your template based off the control's error state.

Example: Adds class="required" when "myError" has the required error.

<div [class.required]="myError.hasError('required')">
  <input type="text" formControlName="username" />
</div>

<div ngxErrors="username" #myError="ngxErrors">
  <div ngxError="required" when="dirty">
    Field is required
  </div>
</div>

You can optionally pass in conditions in which to activate the error.

Example: Adds class="required" when "myError" has the required error and the states are 'dirty' and 'touched'.

<div [class.required]="myError.hasError('required', ['dirty', 'touched'])">
  <input type="text" formControlName="username" />
</div>

<div ngxErrors="username" #myError="ngxErrors">
  <div ngxError="required" when="dirty">
    Field is required
  </div>
</div>

You can also use the "catch-all" selector to get the state of your entire control's validity, alongside on an optional state collection.

<div>
  <div
    [ngClass]="{
    invalid: myError.hasError('*'),
    invalidTouchedDirty: myError.hasError('*', ['touched', 'dirty'])
  }"
  ></div>
  <input type="text" formControlName="username" />
</div>

<div ngxErrors="username" #myError="ngxErrors">
  <div ngxError="required" when="dirty">
    Field is required
  </div>
</div>

isValid(name: string, conditions?: string | string[]): boolean;

The isValid method informs you if a your control is valid, or a property is valid. This can be useful for styling elsewhere in your template based off the control's validity state.

Example: Adds class="valid" when "myError" has no required error.

<div [class.valid]="myError.isValid('required')">
  <input type="text" formControlName="username" />
</div>

<div ngxErrors="username" #myError="ngxErrors">
  <div ngxError="required" when="dirty">
    Field is required
  </div>
</div>

You can optionally pass in conditions in which to evaluate alongside the property you're checking is valid.

Example: Adds class="valid" when "myError" has no required error and the states are 'dirty' and 'touched'.

<div [class.valid]="myError.isValid('required', ['dirty', 'touched'])">
  <input type="text" formControlName="username" />
</div>

<div ngxErrors="username" #myError="ngxErrors">
  <div ngxError="required" when="dirty">
    Field is required
  </div>
</div>

You can also use the "catch-all" selector to check if the control is valid, with no specific error properties, alongside on an optional state collection.

<div>
  <div
    [ngClass]="{
    valid: myError.isValid('*'),
    validTouchedDirty: myError.isValid('*', ['touched', 'dirty'])
  }"
  ></div>
  <input type="text" formControlName="username" />
</div>

<div ngxErrors="username" #myError="ngxErrors">
  <div ngxError="required" when="dirty">
    Field is required
  </div>
</div>

hasErrors: boolean;

The hasErrors property returns true if your control has any number of errors. This can be useful for styling elsewhere in your template on a global control level rather than individual errors.

Example: Adds class="errors" when "myError" has any errors.

<div [class.errors]="myError.hasErrors">
  <input type="text" formControlName="username" />
</div>

<div ngxErrors="username" #myError="ngxErrors">
  <div ngxError="required" when="dirty">
    Field is required
  </div>
  <div ngxError="minlength" when="dirty">
    Min length is 5
  </div>
</div>

errors: { [key: string]: any; };

The errors property returns the object associated with any active errors. This can be used to access any error properties on your control.

Example: Adds Max length is 10, you typed (n) when value is more than 10 characters (based on Validators.maxLength(10)).

<input type="text" formControlName="username" />

<div ngxErrors="username" #myError="ngxErrors">
  <div ngxError="minlength" when="dirty">...</div>
  <div ngxError="maxlength" when="dirty">...</div>
</div>

<div *ngIf="myError.errors?.maxlength">
  Max length is 10, you typed {{ myError.errors.maxlength.actualLength }}
</div>

The errors returned are identical to Angular's FormControl API