silverstripe-cms/client/src/legacy/RedirectorPage.js

import $ from 'jQuery';

$.entwine('ss', function($){
	$('#Form_EditForm_RedirectionType input').entwine({
		onmatch: function() {
			var self = $(this);
			if(self.attr('checked')) this.toggle();
			this._super();
		},
		onunmatch: function() {
			this._super();
		},
		onclick: function() {
			this.toggle();
		},
		toggle: function() {
			if($(this).attr('value') == 'Internal') {
				$('#Form_EditForm_ExternalURL_Holder').hide();
				$('#Form_EditForm_LinkToID_Holder').show();
			} else {
				$('#Form_EditForm_ExternalURL_Holder').show();
				$('#Form_EditForm_LinkToID_Holder').hide();
			}
		}
	});
});