resolve all prefer-const eslint violations

app/assets/javascripts/blob/template_selector.js.es6

-/* eslint-disable comma-dangle, object-shorthand, func-names, space-before-function-paren, arrow-parens, no-unused-vars, class-methods-use-this, no-var, consistent-return, prefer-const, no-param-reassign, space-in-parens, max-len */
+/* eslint-disable comma-dangle, object-shorthand, func-names, space-before-function-paren, arrow-parens, no-unused-vars, class-methods-use-this, no-var, consistent-return, no-param-reassign, space-in-parens, max-len */
 ((global) => {
   class TemplateSelector {
@@ -74,7 +74,7 @@
       if (!file) return;
       const oldValue = this.editor.getValue();
-      let newValue = file.content;
+      const newValue = file.content;
       this.editor.setValue(newValue, 1);
       if (!skipFocus) this.editor.focus();

app/assets/javascripts/boards/mixins/sortable_default_options.js.es6

-/* eslint-disable no-unused-vars, no-mixed-operators, prefer-const, comma-dangle */
+/* eslint-disable no-unused-vars, no-mixed-operators, comma-dangle */
 /* global DocumentTouch */
 ((w) => {
@@ -19,7 +19,7 @@
   gl.issueBoards.touchEnabled = ('ontouchstart' in window) || window.DocumentTouch && document instanceof DocumentTouch;
   gl.issueBoards.getBoardSortableDefaultOptions = (obj) => {
-    let defaultSortOptions = {
+    const defaultSortOptions = {
       animation: 200,
       forceFallback: true,
       fallbackClass: 'is-dragging',

app/assets/javascripts/boards/models/list.js.es6

-/* eslint-disable space-before-function-paren, no-underscore-dangle, class-methods-use-this, consistent-return, prefer-const, space-in-parens, no-shadow, no-param-reassign, max-len, no-unused-vars */
+/* eslint-disable space-before-function-paren, no-underscore-dangle, class-methods-use-this, consistent-return, space-in-parens, no-shadow, no-param-reassign, max-len, no-unused-vars */
 /* global ListIssue */
 /* global ListLabel */
@@ -66,7 +66,7 @@ class List {
   getIssues (emptyIssues = true) {
     const filters = this.filters;
-    let data = { page: this.page };
+    const data = { page: this.page };
     Object.keys(filters).forEach((key) => { data[key] = filters[key]; });

app/assets/javascripts/boards/services/board_service.js.es6

-/* eslint-disable space-before-function-paren, comma-dangle, no-param-reassign, camelcase, prefer-const, max-len, no-unused-vars */
+/* eslint-disable space-before-function-paren, comma-dangle, no-param-reassign, camelcase, max-len, no-unused-vars */
 /* global Vue */
 class BoardService {
@@ -47,7 +47,7 @@ class BoardService {
   }
   getIssuesForList (id, filter = {}) {
-    let data = { id };
+    const data = { id };
     Object.keys(filter).forEach((key) => { data[key] = filter[key]; });
     return this.issues.get(data);

app/assets/javascripts/diff_notes/stores/comments.js.es6

-/* eslint-disable object-shorthand, func-names, camelcase, prefer-const, no-restricted-syntax, guard-for-in, comma-dangle, max-len, no-param-reassign */
+/* eslint-disable object-shorthand, func-names, camelcase, no-restricted-syntax, guard-for-in, comma-dangle, max-len, no-param-reassign */
 /* global Vue */
 /* global DiscussionModel */
@@ -41,7 +41,7 @@
       }
     },
     unresolvedDiscussionIds: function () {
-      let ids = [];
+      const ids = [];
       for (const discussionId in this.state) {
         const discussion = this.state[discussionId];

app/assets/javascripts/due_date_select.js.es6

-/* eslint-disable wrap-iife, func-names, space-before-function-paren, comma-dangle, prefer-template, consistent-return, class-methods-use-this, arrow-body-style, prefer-const, no-unused-vars, no-underscore-dangle, no-new, max-len, no-sequences, no-unused-expressions, no-param-reassign */
+/* eslint-disable wrap-iife, func-names, space-before-function-paren, comma-dangle, prefer-template, consistent-return, class-methods-use-this, arrow-body-style, no-unused-vars, no-underscore-dangle, no-new, max-len, no-sequences, no-unused-expressions, no-param-reassign */
 (function(global) {
   class DueDateSelect {

app/assets/javascripts/issuable.js.es6

-/* eslint-disable no-param-reassign, func-names, no-var, camelcase, no-unused-vars, object-shorthand, space-before-function-paren, no-return-assign, comma-dangle, consistent-return, one-var, one-var-declaration-per-line, quotes, prefer-template, prefer-arrow-callback, prefer-const, wrap-iife, max-len */
+/* eslint-disable no-param-reassign, func-names, no-var, camelcase, no-unused-vars, object-shorthand, space-before-function-paren, no-return-assign, comma-dangle, consistent-return, one-var, one-var-declaration-per-line, quotes, prefer-template, prefer-arrow-callback, wrap-iife, max-len */
 /* global Issuable */
 /* global Turbolinks */
@@ -151,7 +151,7 @@
       this.issuableBulkActions.setOriginalDropdownData();
       if ($checkedIssues.length > 0) {
-        let ids = $.map($checkedIssues, function(value) {
+        const ids = $.map($checkedIssues, function(value) {
           return $(value).data('id');
         });
         $updateIssuesIds.val(ids);

app/assets/javascripts/merge_conflicts/components/diff_file_editor.js.es6

-/* eslint-disable comma-dangle, quote-props, no-useless-computed-key, object-shorthand, prefer-const, no-new, no-param-reassign, max-len */
+/* eslint-disable comma-dangle, quote-props, no-useless-computed-key, object-shorthand, no-new, no-param-reassign, max-len */
 /* global Vue */
 /* global ace */
 /* global Flash */
@@ -50,8 +50,8 @@
         $.get(this.file.content_path)
           .done((file) => {
-            let content = this.$el.querySelector('pre');
-            let fileContent = document.createTextNode(file.content);
+            const content = this.$el.querySelector('pre');
+            const fileContent = document.createTextNode(file.content);
             content.textContent = fileContent.textContent;

app/assets/javascripts/merge_conflicts/merge_conflict_store.js.es6

-/* eslint-disable comma-dangle, object-shorthand, no-param-reassign, camelcase, prefer-const, no-nested-ternary, no-continue, max-len */
+/* eslint-disable comma-dangle, object-shorthand, no-param-reassign, camelcase, no-nested-ternary, no-continue, max-len */
 /* global Cookies */
 /* global Vue */
@@ -251,7 +251,7 @@
     },
     checkLineLengths(linesObj) {
-      let { left, right } = linesObj;
+      const { left, right } = linesObj;
       if (left.length !== right.length) {
         if (left.length > right.length) {
@@ -316,11 +316,11 @@
       let unresolved = 0;
       for (let i = 0, l = files.length; i < l; i += 1) {
-        let file = files[i];
+        const file = files[i];
         if (file.resolveMode === INTERACTIVE_RESOLVE_MODE) {
           let numberConflicts = 0;
-          let resolvedConflicts = Object.keys(file.resolutionData).length;
+          const resolvedConflicts = Object.keys(file.resolutionData).length;
           // We only check for conflicts type 'text'
           // since conflicts `text_editor` can´t be resolved in interactive mode
@@ -364,9 +364,7 @@
       };
       this.state.conflictsData.files.forEach((file) => {
-        let addFile;
-
-        addFile = {
+        const addFile = {
           old_path: file.old_path,
           new_path: file.new_path
         };

app/assets/javascripts/project_label_subscription.js.es6

-/* eslint-disable wrap-iife, func-names, space-before-function-paren, object-shorthand, comma-dangle, one-var, one-var-declaration-per-line, no-restricted-syntax, prefer-const, max-len, no-param-reassign */
+/* eslint-disable wrap-iife, func-names, space-before-function-paren, object-shorthand, comma-dangle, one-var, one-var-declaration-per-line, no-restricted-syntax, max-len, no-param-reassign */
 (function(global) {
   class ProjectLabelSubscription {
@@ -38,8 +38,8 @@
         this.$buttons.attr('data-status', newStatus);
         this.$buttons.find('> span').text(newAction);
-        for (let button of this.$buttons) {
-          let $button = $(button);
+        for (const button of this.$buttons) {
+          const $button = $(button);
           if ($button.attr('data-original-title')) {
             $button.tooltip('hide').attr('data-original-title', newAction).tooltip('fixTitle');

app/assets/javascripts/templates/issuable_template_selector.js.es6

-/* eslint-disable prefer-const, comma-dangle, max-len, no-useless-return, no-param-reassign, max-len */
+/* eslint-disable comma-dangle, max-len, no-useless-return, no-param-reassign, max-len */
 /* global Api */
 /*= require ../blob/template_selector */
@@ -12,7 +12,7 @@
       this.issuableType = this.wrapper.data('issuable-type');
       this.titleInput = $(`#${this.issuableType}_title`);
-      let initialQuery = {
+      const initialQuery = {
         name: this.dropdown.data('selected')
       };

app/assets/javascripts/templates/issuable_template_selectors.js.es6

-/* eslint-disable no-new, comma-dangle, class-methods-use-this, prefer-const, no-param-reassign */
+/* eslint-disable no-new, comma-dangle, class-methods-use-this, no-param-reassign */
 ((global) => {
   class IssuableTemplateSelectors {
@@ -19,7 +19,7 @@
     }
     initEditor() {
-      let editor = $('.markdown-area');
+      const editor = $('.markdown-area');
       // Proxy ace-editor's .setValue to jQuery's .val
       editor.setValue = editor.val;
       editor.getValue = editor.val;

spec/javascripts/activities_spec.js.es6

-/* eslint-disable no-unused-expressions, prefer-const, no-prototype-builtins, no-new, no-shadow, max-len */
+/* eslint-disable no-unused-expressions, no-prototype-builtins, no-new, no-shadow, max-len */
 /*= require js.cookie.js */
 /*= require jquery.endless-scroll.js */
@@ -24,12 +24,12 @@
     }];
   function getEventName(index) {
-    let filter = filters[index];
+    const filter = filters[index];
     return filter.hasOwnProperty('name') ? filter.name : filter.id;
   }
   function getSelector(index) {
-    let filter = filters[index];
+    const filter = filters[index];
     return `#${filter.id}_event_filter`;
   }
@@ -48,8 +48,8 @@
           for (let x = 0; x < filters.length; x += 1) {
             ((x) => {
-              let shouldHighlight = i === x;
-              let testName = shouldHighlight ? 'should highlight' : 'should not highlight';
+              const shouldHighlight = i === x;
+              const testName = shouldHighlight ? 'should highlight' : 'should not highlight';
               it(`${testName} ${getEventName(x)}`, () => {
                 expect($(getSelector(x)).parent().hasClass('active')).toEqual(shouldHighlight);

spec/javascripts/gl_dropdown_spec.js.es6

-/* eslint-disable comma-dangle, prefer-const, no-param-reassign, no-unused-expressions, max-len */
+/* eslint-disable comma-dangle, no-param-reassign, no-unused-expressions, max-len */
 /* global Turbolinks */
 /*= require jquery */
@@ -22,7 +22,7 @@
   let remoteCallback;
-  let navigateWithKeys = function navigateWithKeys(direction, steps, cb, i) {
+  const navigateWithKeys = function navigateWithKeys(direction, steps, cb, i) {
     i = i || 0;
     if (!i) direction = direction.toUpperCase();
     $('body').trigger({
@@ -38,7 +38,7 @@
     }
   };
-  let remoteMock = function remoteMock(data, term, callback) {
+  const remoteMock = function remoteMock(data, term, callback) {
     remoteCallback = callback.bind({}, data);
   };
@@ -89,7 +89,7 @@
       it('should select a following item on DOWN keypress', () => {
         expect($(FOCUSED_ITEM_SELECTOR, this.$dropdownMenuElement).length).toBe(0);
-        let randomIndex = (Math.floor(Math.random() * (this.projectsData.length - 1)) + 0);
+        const randomIndex = (Math.floor(Math.random() * (this.projectsData.length - 1)) + 0);
         navigateWithKeys('down', randomIndex, () => {
           expect($(FOCUSED_ITEM_SELECTOR, this.$dropdownMenuElement).length).toBe(1);
           expect($(`${ITEM_SELECTOR}:eq(${randomIndex}) a`, this.$dropdownMenuElement)).toHaveClass('is-focused');
@@ -100,7 +100,7 @@
         expect($(FOCUSED_ITEM_SELECTOR, this.$dropdownMenuElement).length).toBe(0);
         navigateWithKeys('down', (this.projectsData.length - 1), () => {
           expect($(FOCUSED_ITEM_SELECTOR, this.$dropdownMenuElement).length).toBe(1);
-          let randomIndex = (Math.floor(Math.random() * (this.projectsData.length - 2)) + 0);
+          const randomIndex = (Math.floor(Math.random() * (this.projectsData.length - 2)) + 0);
           navigateWithKeys('up', randomIndex, () => {
             expect($(FOCUSED_ITEM_SELECTOR, this.$dropdownMenuElement).length).toBe(1);
             expect($(`${ITEM_SELECTOR}:eq(${((this.projectsData.length - 2) - randomIndex)}) a`, this.$dropdownMenuElement)).toHaveClass('is-focused');
@@ -110,14 +110,14 @@
       it('should click the selected item on ENTER keypress', () => {
         expect(this.dropdownContainerElement).toHaveClass('open');
-        let randomIndex = Math.floor(Math.random() * (this.projectsData.length - 1)) + 0;
+        const randomIndex = Math.floor(Math.random() * (this.projectsData.length - 1)) + 0;
         navigateWithKeys('down', randomIndex, () => {
           spyOn(Turbolinks, 'visit').and.stub();
           navigateWithKeys('enter', null, () => {
             expect(this.dropdownContainerElement).not.toHaveClass('open');
-            let link = $(`${ITEM_SELECTOR}:eq(${randomIndex}) a`, this.$dropdownMenuElement);
+            const link = $(`${ITEM_SELECTOR}:eq(${randomIndex}) a`, this.$dropdownMenuElement);
             expect(link).toHaveClass('is-active');
-            let linkedLocation = link.attr('href');
+            const linkedLocation = link.attr('href');
             if (linkedLocation && linkedLocation !== '#') expect(Turbolinks.visit).toHaveBeenCalledWith(linkedLocation);
           });
         });
@@ -171,9 +171,8 @@
       });
     });
-
     it('should still have input value on close and restore', () => {
-      let $searchInput = $(SEARCH_INPUT_SELECTOR);
+      const $searchInput = $(SEARCH_INPUT_SELECTOR);
       initDropDown.call(this, false, true);
       $searchInput
         .trigger('focus')

spec/javascripts/labels_issue_sidebar_spec.js.es6

-/* eslint-disable no-new, prefer-const */
+/* eslint-disable no-new */
 /* global IssuableContext */
 /* global LabelsSelect */
@@ -33,7 +33,7 @@
             LABELS_DATA.push({ id: i, title: `test ${i}`, color: '#5CB85C' });
           }
         } else if (req.url === '/root/test/issues/2.json') {
-          let tmp = [];
+          const tmp = [];
           for (let i = 0; i < saveLabelCount; i += 1) {
             tmp.push({ id: i, title: `test ${i}`, color: '#5CB85C' });
           }