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).

client/components/main/editor.js

@@ -1,7 +1,7 @@
-var dropdownMenuIsOpened = false;
+let dropdownMenuIsOpened = false;
 
-Template.editor.onRendered(function() {
-  var $textarea = this.$('textarea');
+Template.editor.onRendered(() => {
+  const $textarea = this.$('textarea');
 
   autosize($textarea);
 
@@ -9,39 +9,40 @@ Template.editor.onRendered(function() {
     // Emojies
     {
       match: /\B:([\-+\w]*)$/,
-      search: function(term, callback) {
-        callback($.map(Emoji.values, function(emoji) {
+      search(term, callback) {
+        callback($.map(Emoji.values, (emoji) => {
           return emoji.indexOf(term) === 0 ? emoji : null;
         }));
       },
-      template: function(value) {
-        var image = '<img src="' + Emoji.baseImagePath + value + '.png"></img>';
+      template(value) {
+        const imgSrc = Emoji.baseImagePath + value;
+        const image = `<img src="${imgSrc}.png" />`;
         return image + value;
       },
-      replace: function(value) {
-        return ':' + value + ':';
+      replace(value) {
+        return `:${value}:`;
       },
-      index: 1
+      index: 1,
     },
 
     // User mentions
     {
       match: /\B@(\w*)$/,
-      search: function(term, callback) {
-        var currentBoard = Boards.findOne(Session.get('currentBoard'));
-        callback($.map(currentBoard.members, function(member) {
-          var username = Users.findOne(member.userId).username;
+      search(term, callback) {
+        const currentBoard = Boards.findOne(Session.get('currentBoard'));
+        callback($.map(currentBoard.members, (member) => {
+          const username = Users.findOne(member.userId).username;
           return username.indexOf(term) === 0 ? username : null;
         }));
       },
-      template: function(value) {
+      template(value) {
         return value;
       },
-      replace: function(username) {
-        return '@' + username + ' ';
+      replace(username) {
+        return `@${username} `;
       },
-      index: 1
-    }
+      index: 1,
+    },
   ]);
 
   // Since commit d474017 jquery-textComplete automatically closes a potential
@@ -51,27 +52,27 @@ Template.editor.onRendered(function() {
   // 'open' and 'hide' events, and create a ghost escapeAction when the dropdown
   // is opened (and rely on textComplete to execute the actual action).
   $textarea.on({
-    'textComplete:show': function() {
+    'textComplete:show'() {
       dropdownMenuIsOpened = true;
     },
-    'textComplete:hide': function() {
-      Tracker.afterFlush(function() {
+    'textComplete:hide'() {
+      Tracker.afterFlush(() => {
         dropdownMenuIsOpened = false;
       });
-    }
+    },
   });
 });
 
 EscapeActions.register('textcomplete',
-  function() {},
-  function() { return dropdownMenuIsOpened; }
+  () => {},
+  () => dropdownMenuIsOpened
 );
 
 Template.viewer.events({
   // Viewer sometimes have click-able wrapper around them (for instance to edit
   // the corresponding text). Clicking a link shouldn't fire these actions, stop
   // we stop these event at the viewer component level.
-  'click a': function(evt) {
+  'click a'(evt) {
     evt.stopPropagation();
 
     // XXX We hijack the build-in browser action because we currently don't have
@@ -79,7 +80,7 @@ Template.viewer.events({
     // handled by a third party package that we can't configure easily. Fix that
     // by using directly `_blank` attribute in the rendered HTML.
     evt.preventDefault();
-    let href = evt.currentTarget.href;
+    const href = evt.currentTarget.href;
     window.open(href, '_blank');
-  }
+  },
 });