core_form/changechecker

This module provides change detection to forms, allowing a browser to warn the user before navigating away if changes have been made.

Two flags are stored for each form:

  • a 'dirty' flag; and
  • a 'submitted' flag.

When the page is unloaded each watched form is checked. If the 'dirty' flag is set for any form, and the 'submitted' flag is not set for any form, then a warning is shown.

The 'dirty' flag is set when any form element is modified within a watched form. The flag can also be set programatically. This may be required for custom form elements.

It is not possible to customise the warning message in any modern browser.

Please note that some browsers have controls on when these alerts may or may not be shown. See https://developer.mozilla.org/en-US/docs/Web/API/WindowEventHandlers/onbeforeunload for browser-specific notes and references.

Source:
Copyright:
  • 2021 Andrew Lyons
License:
  • http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
Examples

Usage where the FormElement is already held

import {watchForm} from 'core_form/changechecker';

// Fetch the form element somehow.
watchForm(formElement);

Usage from the child of a form - i.e. an input, button, div, etc.

import {watchForm} from 'core_form/changechecker';

// Watch the form by using a child of it.
watchForm(document.querySelector('input[data-foo="bar"]'););

Usage from within a template

<form id="mod_example-entry-{{uniqid}}" ...>
  <!--

  -->
</form>
{{#js}}
require(['core_form/changechecker'], function(changeChecker) {
    watchFormById('mod_example-entry-{{uniqid}}');
});
{{/js}}

Methods

(static) disableAllChecks()

Source:

Actively disable the form change checker.

Please note that it cannot be re-enabled once disabled.

(static) isAnyWatchedFormDirty() → {Bool}

Source:

Check whether any watched from is dirty.

Returns:
Type
Bool

(static) markAllFormsAsDirty()

Source:

Mark all forms as dirty.

This function is only for backwards-compliance with the old YUI module and should not be used in any other situation. It will be removed in Moodle 4.4.

(static) markAllFormsSubmitted()

Source:

Mark all forms as submitted.

This function is only for backwards-compliance with the old YUI module and should not be used in any other situation. It will be removed in Moodle 4.4.

(static) markFormAsDirty(formNode)

Source:

Mark a specific form as dirty.

This behaviour may be required for custom form elements which are not caught by the standard change listeners.

Parameters:
Name Type Description
formNode HTMLElement

(static) markFormAsDirtyById(formId)

Source:

Mark the form matching the specified ID as dirty.

Parameters:
Name Type Description
formId String

(static) markFormChangedFromNode(changedNode)

Source:

Mark a form as changed.

Parameters:
Name Type Description
changedNode HTMLElement

An element in the form which was changed

(static) markFormSubmitted(formNode)

Source:

Mark a form as submitted.

Parameters:
Name Type Description
formNode HTMLElement

An element in the form to mark as submitted

(static) resetAllFormDirtyStates()

Source:

Reset the 'dirty' flag for all watched forms.

If a form was previously marked as 'dirty', then this flag will be cleared and when the page is unloaded no warning will be shown.

(static) resetFormDirtyState(formNode)

Source:

Reset the 'dirty' flag of the specified form.

Parameters:
Name Type Description
formNode HTMLElement

(static) resetFormDirtyStateById(formId)

Source:

Reset the dirty state of the form matching the specified ID..

Parameters:
Name Type Description
formId String

(protected, static) startWatching()

Source:

Start watching for form changes.

This function is called on module load, and should not normally be called.

(static) unWatchForm(formNode)

Source:

Stop watching the specified form for changes.

If the form was not watched, then no change is made.

A child of the form may be passed instead.

Example

Stop watching a form for changes

import {unWatchForm} from 'core_form/changechecker';

// ...
document.addEventListener('click', e => {
    if (e.target.closest('[data-action="changePage"]')) {
        unWatchForm(e.target);
    }
});
Parameters:
Name Type Description
formNode HTMLElement

(static) watchForm(formNode)

Source:

Watch the specified form for changes.

Parameters:
Name Type Description
formNode HTMLElement

(static) watchFormById(formId)

Source:

Watch the form matching the specified ID for changes.

Parameters:
Name Type Description
formId String