add "bulk-detach" option to recurring events from events-manager wordpress plugin

bulk-detach-recurring-events.js

// ==UserScript==
// @name         Bulk-Detach option for Recurring-Events
// @namespace    https://wordpress.org/support/plugin/events-manager/
// @version      0.1
// @description  allow bulk-detach of recurring events for Wordpress Events-Manager plugin
// @author       Marc Günther
// @match        *://*/*wp-admin/edit.php?post_type=event&scope=all&recurrence_id=*
// @grant        none
// ==/UserScript==

/**
 * TamperMonkey script which adds a new button "Detach" to the upper "Bulk Actions" popup menu in the Events-Manager Wordpress plugin.
 * To use:
 * - Events -> Recurring Events
 * - Edit one of the events.
 * - In the event, click on "You can edit individual recurrences and disassociate them with this recurring event."
 * - Now you get a list of all single events, and have a new "Detach" option in "Bulk actions".
 * - Selecting it will detach all selected events one by one.
 *
 * Implementation:
 * - Store ids of all selected checkboxes in sessionStorage.
 * - Iterate through all of them, and click the corresponding "Detach" link.
 * - When no checkboxes are left, delete the entry from sessionStorage.
 */
(function() {
    'use strict';

    var storage_key = "dismiss-checkbox-ids";

    // detach events belonging to comma separated checkbox ids
    function detach(checkbox_ids) {
        for (var checkbox_id of checkbox_ids.split(",")) {
            // find the checkbox
            var checkbox = document.getElementById(checkbox_id);
            if (checkbox) {
                // find the "Detach" link
                var detach_link = checkbox.parentNode.parentNode.querySelector("a.em-detach-link");
                if (detach_link) {
                    // disable confirmation popup and click the link
                    window.confirm = () => true;
                    detach_link.click();
                    return false;
                }
            }
        }
        // remove from sessionStorage after we are done
        sessionStorage.removeItem(storage_key);
    }

    // add the "Detach" option to the upper "Bulk Actions"
    var detach_option = document.createElement("option");
    detach_option.text = "Detach";
    document.querySelector("select#bulk-action-selector-top").add(detach_option);

    // patch the "Apply" button to check for our new "Detach" option
    document.querySelector("input#doaction.action.button").onclick = () => {
        if (document.querySelector("select#bulk-action-selector-top").value == "Detach") {
            // find ids of all selected checkboxes
            var selected_checkboxes = [...document.querySelectorAll("input[type='checkbox'][id*='cb-select-']:checked")].map(el=>el.id).join(",");
            // store them in the sessionStorage
            sessionStorage.setItem(storage_key, selected_checkboxes);
            // and start detaching the first (the rest will be detached after reload of this page)
            detach(selected_checkboxes);
            return false;
        }
        // perform original action, whatever it is
        return true;
    }

    // look into the session storage if we still have items to detach, and do so
    var selected_checkboxes = sessionStorage.getItem(storage_key);
    if (selected_checkboxes) {
        detach(selected_checkboxes);
    }
})();