clean code

resource/js/app.js

@@ -56,8 +56,7 @@ let pageIdOnHackmd = null;
 let pagePath;
 let pageContent = '';
 let markdown = '';
-let pageGrant = null;
-let slackChannels = '';
+let slackChannels;
 if (mainContent !== null) {
   pageId = mainContent.getAttribute('data-page-id');
   pageRevisionId = mainContent.getAttribute('data-page-revision-id');
@@ -65,7 +64,7 @@ if (mainContent !== null) {
   pageRevisionIdHackmdSynced = mainContent.getAttribute('data-page-revision-id-hackmd-synced') || null;
   pageIdOnHackmd = mainContent.getAttribute('data-page-id-on-hackmd') || null;
   pagePath = mainContent.attributes['data-path'].value;
-  slackChannels = mainContent.getAttribute('data-slack-channels');
+  slackChannels = mainContent.getAttribute('data-slack-channels') || '';
   const rawText = document.getElementById('raw-text-original');
   if (rawText) {
     pageContent = rawText.innerHTML;

resource/js/components/SlackNotification.js

@@ -76,3 +76,7 @@ SlackNotification.propTypes = {
   slackChannels: PropTypes.string,
   formName: PropTypes.string,
 };
+
+SlackNotification.defaultProps = {
+  slackChannels: '',
+};