useFormPristine

Returns whether a FormGroup is pristine (has not been modified) as a signal. The signal updates reactively whenever the form's pristine state changes.

Usage

import { useFormPristine } from 'ng-reactive-utils';

@Component({
  template: `
    <form [formGroup]="form">
      <input formControlName="name" />

      @if (isPristine()) {
        <p class="hint">Start typing to make changes</p>
      } @else {
        <p class="info">Form has been modified</p>
      }
    </form>
  `,
})
class SimpleFormComponent {
  form = new FormGroup({
    name: new FormControl(''),
  });

  isPristine = useFormPristine(this.form);
}

Parameters

Parameter	Type	Default	Description
form	FormGroup	required	The FormGroup to check pristine state for

Returns

Signal<boolean> - A readonly signal containing the pristine state (true if not modified)

Notes

• Uses toSignal with form.valueChanges observable
• Returns true when no control has been modified
• Returns false when any control value has been changed
• Opposite of useFormDirty

Source

import { Signal } from '@angular/core';
import { toSignal } from '@angular/core/rxjs-interop';
import { FormGroup } from '@angular/forms';
import { map } from 'rxjs';

/**
 * Returns whether a FormGroup is pristine (has not been modified) as a signal.
 * The signal updates reactively whenever the form's pristine state changes.
 *
 * @param form - The FormGroup to check pristine state for
 * @returns A signal containing the pristine state (true if not modified)
 *
 * @example
 * ```typescript
 * @Component({
 *   template: `
 *     <form [formGroup]="form">
 *       <input formControlName="name" />
 *       @if (isPristine()) {
 *         <span>Form has not been modified</span>
 *       }
 *     </form>
 *   `
 * })
 * class MyComponent {
 *   form = new FormGroup({
 *     name: new FormControl('')
 *   });
 *   isPristine = useFormPristine(this.form);
 * }
 * ```
 */
export const useFormPristine = (form: FormGroup): Signal<boolean> => {
  return toSignal(form.valueChanges.pipe(map(() => form.pristine)), {
    initialValue: form.pristine,
  }) as Signal<boolean>;
};