[ci skip] Add constants

app/assets/javascripts/notes/components/issue_comment_form.vue

 <script>
 /* global Flash */
 
-import userAvatarLink from '../../vue_shared/components/user_avatar/user_avatar_link.vue';
-import markdownField from '../../vue_shared/components/markdown/field.vue';
-import issueNoteSignedOutWidget from './issue_note_signed_out_widget.vue';
-import eventHub from '../event_hub';
+  import userAvatarLink from '../../vue_shared/components/user_avatar/user_avatar_link.vue';
+  import markdownField from '../../vue_shared/components/markdown/field.vue';
+  import issueNoteSignedOutWidget from './issue_note_signed_out_widget.vue';
+  import eventHub from '../event_hub';
+  import * as constants from '../constants';
 
-export default {
+  export default {
     data() {
       const { create_note_path, state } = window.gl.issueData;
       const { currentUserData } = window.gl;
@@ -15,7 +16,7 @@ export default {
         note: '',
         markdownDocsUrl: '',
         markdownPreviewUrl: gl.issueData.preview_note_path,
-      noteType: 'comment',
+        noteType: constants.COMMENT,
         issueState: state,
         endpoint: create_note_path,
         author: currentUserData,
@@ -31,16 +32,16 @@ export default {
         return window.gon.current_user_id;
       },
       commentButtonTitle() {
-      return this.noteType === 'comment' ? 'Comment' : 'Start discussion';
+        return this.noteType === constants.COMMENT ? 'Comment' : 'Start discussion';
       },
       isIssueOpen() {
-      return this.issueState === 'opened' || this.issueState === 'reopened';
+        return this.issueState === constants.OPENED || this.issueState === constants.REOPENED;
       },
       issueActionButtonTitle() {
         if (this.note.length) {
           const actionText = this.isIssueOpen ? 'close' : 'reopen';
 
-        return this.noteType === 'comment' ? `Comment & ${actionText} issue` : `Start discussion & ${actionText} issue`;
+          return this.noteType === constants.COMMENT ? `Comment & ${actionText} issue` : `Start discussion & ${actionText} issue`;
         }
 
         return this.isIssueOpen ? 'Close issue' : 'Reopen issue';
@@ -74,8 +75,8 @@ export default {
             },
           };
 
-        if (this.noteType === 'discussion') {
-          noteData.data.note.type = 'DiscussionNote';
+          if (this.noteType === constants.DISCUSSION) {
+            noteData.data.note.type = constants.DISCUSSION_NOTE;
           }
 
           this.$store.dispatch('saveNote', noteData)
@@ -97,11 +98,11 @@ export default {
 
         if (withIssueAction) {
           if (this.isIssueOpen) {
-          gl.issueData.state = 'closed';
-          this.issueState = 'closed';
+            gl.issueData.state = constants.CLOSED;
+            this.issueState = constants.CLOSED;
           } else {
-          gl.issueData.state = 'reopened';
-          this.issueState = 'reopened';
+            gl.issueData.state = constants.REOPENED;
+            this.issueState =constants.REOPENED;
           }
           this.isIssueOpen = !this.isIssueOpen;
 
@@ -146,10 +147,14 @@ export default {
       this.markdownDocsUrl = issueData.markdownDocs;
 
       eventHub.$on('issueStateChanged', (isClosed) => {
-      this.issueState = isClosed ? 'closed' : 'reopened';
+        this.issueState = isClosed ? constants.CLOSED : constants.REOPENED;
       });
     },
-};
+
+    destroyed() {
+      eventHub.$off('issueStateChanged');
+    }
+  };
 </script>
 
 <template>
@@ -167,7 +172,8 @@ export default {
               :link-href="author.path"
               :img-src="author.avatar_url"
               :img-alt="author.name"
-              :img-size="40" />
+              :img-size="40"
+              />
           </div>
           <div class="js-main-target-form timeline-content timeline-content-form common-note-form">
             <markdown-field

app/assets/javascripts/notes/constants.js

+export const DISCUSSION_NOTE = 'DiscussionNote';
+export const DISCUSSION = 'discussion';
+export const NOTE = 'note';
+export const SYSTEM_NOTE = 'systemNote';
+export const COMMENT = 'comment';
+export const OPENED = 'opened';
+export const REOPENED = 'reopened';
+export const CLOSED = 'closed';
\ No newline at end of file

app/assets/javascripts/notes/stores/actions.js

 /* global Flash */
 
 import * as types from './mutation_types';
-import * as utils from './issue_notes_utils';
+import * as utils from './utils';
+import * as constants from '../constants';
 import service from '../services/issue_notes_service';
 import loadAwardsHandler from '../../awards_handler';
 import sidebarTimeTrackingEventHub from '../../sidebar/event_hub';
@@ -147,7 +148,7 @@ export const poll = ({ commit, state, getters }) => {
         res.notes.forEach((note) => {
           if (notesById[note.id]) {
             commit(types.UPDATE_NOTE, note);
-          } else if (note.type === 'DiscussionNote') {
+          } else if (note.type === constants.DISCUSSION_NOTE) {
             const discussion = utils.findNoteObjectById(state.notes, note.discussion_id);
 
             if (discussion) {

app/assets/javascripts/notes/stores/mutations.js

 import * as utils from './utils';
 import * as types from './mutation_types';
+import * as constants from '../constants';
 
 export default {
   [types.ADD_NEW_NOTE](state, note) {
@@ -7,7 +8,7 @@ export default {
     const noteData = {
       expanded: true,
       id: discussion_id,
-      individual_note: !(type === 'DiscussionNote'),
+      individual_note: !(type === constants.DISCUSSION_NOTE),
       notes: [note],
       reply_id: discussion_id,
     };
@@ -78,7 +79,7 @@ export default {
     notesArr.push({
       individual_note: true,
       isPlaceholderNote: true,
-      placeholderType: data.isSystemNote ? 'systemNote' : 'note',
+      placeholderType: data.isSystemNote ? constants.SYSTEM_NOTE : constants.NOTE,
       notes: [
         {
           body: data.noteBody,