Craft CMS - Sidebar Entry Types plugin: change the 'New entry' button to create an entry in the selected section and entry type.

cp-custom.js

(function() {

    // on click of sidebar entry type
    document.addEventListener('click', function (event) {
        if (event.target.parentNode && event.target.parentNode.matches('a[data-entry-type].sel')) {
            setTimeout(function () {
                manageNewEntryButton(event.target.parentNode);
            }, 10);
        }
    }, false);

    // on initial load
    setTimeout(function () {
        var selectedEntryTypeListing = document.querySelector('a.sel[data-entry-type]');
        if (selectedEntryTypeListing) {
            manageNewEntryButton(selectedEntryTypeListing);
        }
    }, 10);

    // Change 'New entry' button so it creates a new entry using the entry type selected in the sidebar
    function manageNewEntryButton(elm) {
        var newEntryButtonWrapper = document.querySelector('#action-buttons div[data-wrapper]');
        if (newEntryButtonWrapper) {
            var buttonLabelText = "New entry";
            var button = newEntryButtonWrapper.querySelector('button');
            if (button) {
                var buttonLabel = button.querySelector('.label');
                if (buttonLabel) {
                    buttonLabelText = buttonLabel.textContent;
                }
                button.innerHTML = null;
                button.classList.remove('icon');
                var newEntryByTypeButton = document.createElement('a');
                newEntryByTypeButton.classList.add('btn', 'submit', 'add', 'icon');

                var newEntryByTypeLabel = document.createElement('div');
                newEntryByTypeLabel.classList.add('label');
                newEntryByTypeLabel.textContent = buttonLabelText;
                var newEntryByTypeSpinner = document.createElement('div');
                newEntryByTypeSpinner.classList.add('spinner', 'spinner-absolute');

                newEntryByTypeButton.appendChild(newEntryByTypeLabel);
                newEntryByTypeButton.appendChild(newEntryByTypeSpinner);

                // Add href to create a new entry of the selected type
                var seg1 = location.pathname.split('/')[1];
                var section = elm.dataset.section;
                var typeId = elm.dataset.typeid;
                newEntryByTypeButton.href = '/' + seg1 + '/actions/entries/create?section=' + section + '&typeId=' + typeId;
                newEntryButtonWrapper.prepend(newEntryByTypeButton);
            }
        }
    }
})();