Enforce a consistent ES6 coding style

Replace the old (and broken) jshint + jscsrc by eslint and configure
it to support some of the ES6 features.

The command `eslint` currently has one error which is a bug that was
discovered by its static analysis and should be fixed (usage of a
dead object).

server/migrations.js

@@ -11,35 +11,35 @@
 //
 // To prevent this bug we always have to disable the schema validation and
 // argument transformations. We generally use the shorthandlers defined below.
-var noValidate = {
+const noValidate = {
   validate: false,
   filter: false,
   autoConvert: false,
   removeEmptyStrings: false,
-  getAutoValues: false
+  getAutoValues: false,
 };
-var noValidateMulti = _.extend(noValidate, { multi: true });
+const noValidateMulti = { ...noValidate, multi: true };
 
-Migrations.add('board-background-color', function() {
-  var defaultColor = '#16A085';
+Migrations.add('board-background-color', () => {
+  const defaultColor = '#16A085';
   Boards.update({
     background: {
-      $exists: false
-    }
+      $exists: false,
+    },
   }, {
     $set: {
       background: {
         type: 'color',
-        color: defaultColor
-      }
-    }
+        color: defaultColor,
+      },
+    },
   }, noValidateMulti);
 });
 
-Migrations.add('lowercase-board-permission', function() {
-  _.forEach(['Public', 'Private'], function(permission) {
+Migrations.add('lowercase-board-permission', () => {
+  _.forEach(['Public', 'Private'], (permission) => {
     Boards.update(
-      { permission: permission },
+      { permission },
       { $set: { permission: permission.toLowerCase() } },
       noValidateMulti
     );
@@ -47,23 +47,23 @@ Migrations.add('lowercase-board-permission', function() {
 });
 
 // Security migration: see https://github.com/wekan/wekan/issues/99
-Migrations.add('change-attachments-type-for-non-images', function() {
-  var newTypeForNonImage = 'application/octet-stream';
-  Attachments.find().forEach(function(file) {
-    if (! file.isImage()) {
+Migrations.add('change-attachments-type-for-non-images', () => {
+  const newTypeForNonImage = 'application/octet-stream';
+  Attachments.find().forEach((file) => {
+    if (!file.isImage()) {
       Attachments.update(file._id, {
         $set: {
           'original.type': newTypeForNonImage,
-          'copies.attachments.type': newTypeForNonImage
-        }
+          'copies.attachments.type': newTypeForNonImage,
+        },
       }, noValidate);
     }
   });
 });
 
-Migrations.add('card-covers', function() {
-  Cards.find().forEach(function(card) {
-    var cover =  Attachments.findOne({ cardId: card._id, cover: true });
+Migrations.add('card-covers', () => {
+  Cards.find().forEach((card) => {
+    const cover =  Attachments.findOne({ cardId: card._id, cover: true });
     if (cover) {
       Cards.update(card._id, {$set: {coverId: cover._id}}, noValidate);
     }
@@ -71,54 +71,54 @@ Migrations.add('card-covers', function() {
   Attachments.update({}, {$unset: {cover: ''}}, noValidateMulti);
 });
 
-Migrations.add('use-css-class-for-boards-colors', function() {
-  var associationTable = {
+Migrations.add('use-css-class-for-boards-colors', () => {
+  const associationTable = {
     '#27AE60': 'nephritis',
     '#C0392B': 'pomegranate',
     '#2980B9': 'belize',
     '#8E44AD': 'wisteria',
     '#2C3E50': 'midnight',
-    '#E67E22': 'pumpkin'
+    '#E67E22': 'pumpkin',
   };
-  Boards.find().forEach(function(board) {
-    var oldBoardColor = board.background.color;
-    var newBoardColor = associationTable[oldBoardColor];
+  Boards.find().forEach((board) => {
+    const oldBoardColor = board.background.color;
+    const newBoardColor = associationTable[oldBoardColor];
     Boards.update(board._id, {
       $set: { color: newBoardColor },
-      $unset: { background: '' }
+      $unset: { background: '' },
     }, noValidate);
   });
 });
 
-Migrations.add('denormalize-star-number-per-board', function() {
-  Boards.find().forEach(function(board) {
-    var nStars = Users.find({'profile.starredBoards': board._id}).count();
+Migrations.add('denormalize-star-number-per-board', () => {
+  Boards.find().forEach((board) => {
+    const nStars = Users.find({'profile.starredBoards': board._id}).count();
     Boards.update(board._id, {$set: {stars: nStars}}, noValidate);
   });
 });
 
 // We want to keep a trace of former members so we can efficiently publish their
 // infos in the general board publication.
-Migrations.add('add-member-isactive-field', function() {
-  Boards.find({}, {fields: {members: 1}}).forEach(function(board) {
-    var allUsersWithSomeActivity = _.chain(
-      Activities.find({boardId: board._id}, {fields:{userId:1}}).fetch())
+Migrations.add('add-member-isactive-field', () => {
+  Boards.find({}, {fields: {members: 1}}).forEach((board) => {
+    const allUsersWithSomeActivity = _.chain(
+      Activities.find({ boardId: board._id }, { fields:{ userId:1 }}).fetch())
         .pluck('userId')
         .uniq()
         .value();
-    var currentUsers = _.pluck(board.members, 'userId');
-    var formerUsers = _.difference(allUsersWithSomeActivity, currentUsers);
+    const currentUsers = _.pluck(board.members, 'userId');
+    const formerUsers = _.difference(allUsersWithSomeActivity, currentUsers);
 
-    var newMemberSet = [];
-    _.forEach(board.members, function(member) {
+    const newMemberSet = [];
+    _.forEach(board.members, (member) => {
       member.isActive = true;
       newMemberSet.push(member);
     });
-    _.forEach(formerUsers, function(userId) {
+    _.forEach(formerUsers, (userId) => {
       newMemberSet.push({
-        userId: userId,
+        userId,
         isAdmin: false,
-        isActive: false
+        isActive: false,
       });
     });
     Boards.update(board._id, {$set: {members: newMemberSet}}, noValidate);