Use const when variable never reassigned

Test plan:
  - Existing test pass

Refs DE-1426

flag=none

Change-Id: I01a3a0eec63c79c154089c6b7935201032ef5113
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/303158
Reviewed-by: Paulo Chaves <paulo.chaves@instructure.com>
Reviewed-by: Derek Williams <derek.williams@instructure.com>
QA-Review: Aaron Shafovaloff <ashafovaloff@instructure.com>
Product-Review: Cameron Ray <cameron.ray@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>

ui/features/collaborations/jquery/index.js

@@ -115,10 +115,10 @@ CollaborationsPage.Events = {
   },
 
   onTypeChange(_e) {
-    let name = $(this).val(),
-      type = name,
-      launch_url = $(this).find('option:selected').data('launch-url'),
-      $description
+    const name = $(this).val()
+    let type = name
+    const launch_url = $(this).find('option:selected').data('launch-url')
+    let $description
 
     if (launch_url) {
       $('.collaborate_data, #google_docs_description').hide()

ui/features/course_settings/jquery/index.js

@@ -85,7 +85,6 @@ var GradePublishing = {
     })
   },
   publish() {
-    let confirmMessage
     if (
       GradePublishing.status === 'publishing' ||
       GradePublishing.status === 'pending' ||
@@ -94,7 +93,7 @@ var GradePublishing = {
       return
     }
 
-    confirmMessage =
+    const confirmMessage =
       GradePublishing.status === 'published'
         ? I18n.t('Are you sure you want to resync these grades to the student information system?')
         : I18n.t(

ui/features/epub_exports/react/CourseListItem.js

@@ -63,12 +63,10 @@ class CourseListItem extends React.Component {
   }
 
   getDisplayTimestamp = () => {
-    let timestamp
-
     if (_.isEmpty(this.epubExport())) {
       return null
     }
-    timestamp = this.epubExport().updated_at
+    const timestamp = this.epubExport().updated_at
 
     return <FriendlyDatetime dateTime={timestamp} />
   }

ui/features/external_apps/react/components/AddApp.js

@@ -89,10 +89,10 @@ export default createReactClass({
   },
 
   handleChange(e) {
-    let target = e.target,
-      value = target.value,
-      name = $(target).data('rel'),
-      fields = this.state.fields
+    const target = e.target
+    let value = target.value
+    const name = $(target).data('rel')
+    const fields = this.state.fields
 
     if (target.type === 'checkbox') {
       value = target.checked

ui/features/learning_mastery/backbone/views/SectionMenuView.js

@@ -74,8 +74,8 @@ class SectionMenuView extends View {
       return e.preventDefault()
     })
     return this.$('.section-select-menu').on('menuselect', (event, ui) => {
-      let section
-      section = this.$('[aria-checked=true] input[name=section_to_show_radio]').val() || undefined
+      const section =
+        this.$('[aria-checked=true] input[name=section_to_show_radio]').val() || undefined
       $.publish('currentSection/change', [section, this.cid])
       return this.trigger('menuselect', event, ui, this.currentSection)
     })

ui/features/theme_editor/react/ThemeEditor.js

@@ -172,7 +172,8 @@ export default class ThemeEditor extends React.Component {
   }
 
   handleThemeStateChange = (key, value, opts = {}) => {
-    let {files, properties} = this.state.themeStore
+    const {files} = this.state.themeStore
+    let {properties} = this.state.themeStore
     if (value instanceof File) {
       const fileStorageObject = {
         variable_name: key,