Changed to global keycodes, refactored for quality

lms/static/js/my_courses_dropdown.js

-$(document).ready(function() {
+(function(require) {
     'use strict';
 
+    require([
+        'jquery',
+        'edx-ui-toolkit/js/utils/constants'
+    ], function($, constants) {
          // define variables for code legibility
-    var dropdownMenuToggle = $('.dropdown');
-    var dropdownMenu = $('.dropdown-menu');
-    var menuItems = dropdownMenu.find('a');
-
-    var keyCodes = {
-        leftArrow: 37,
-        upArrow: 38,
-        rightArrow: 39,
-        downArrow: 40,
-        tab: 9,
-        escape: 27,
-        space: 32
-    };
-
+        var $dropdownMenuToggle = $('.dropdown');
+        var $dropdownMenu = $('.dropdown-menu');
+        var menuItems = $dropdownMenu.find('a');
 
         // bind menu toggle click for later use
-    dropdownMenuToggle.toggle(function() {
-        dropdownMenu.addClass('expanded').find('a').first().focus();
-        dropdownMenuToggle.addClass('active').attr('aria-expanded', 'true');
+        $dropdownMenuToggle.toggle(function() {
+            $dropdownMenu.addClass('expanded').find('a').first()
+                .focus();
+            $dropdownMenuToggle.addClass('active').attr('aria-expanded', 'true');
         }, function() {
-        dropdownMenu.removeClass('expanded');
-        dropdownMenuToggle.removeClass('active').attr('aria-expanded', 'false').focus();
+            $dropdownMenu.removeClass('expanded');
+            $dropdownMenuToggle.removeClass('active').attr('aria-expanded', 'false').focus();
         });
 
         // catch keypresses when focused on dropdownMenuToggle (we only care about spacebar keypresses here)
-    dropdownMenuToggle.on('keydown', function(event) {
+        $dropdownMenuToggle.on('keydown', function(event) {
             // if space key pressed
-        if (event.which === keyCodes.space) {
-            dropdownMenuToggle.click();
+            if (event.which === constants.keyCodes.space) {
+                $dropdownMenuToggle.click();
                 event.preventDefault();
             }
         });
 
-    // catch keypresses when inside dropdownMenu
-    // (we want to catch spacebar; escape; up arrow or shift+tab; and down arrow or tab)
-    dropdownMenu.on('keydown', function(event) {
-        catchKeyPress($(this), event);
-    });
-
         function catchKeyPress(object, event) {
             // get currently focused item
             var focusedItem = jQuery(':focus');
@@ -55,20 +43,20 @@ $(document).ready(function() {
             var itemToFocusIndex;
 
             // if space key pressed
-        if (event.which === keyCodes.space) {
-            dropdownMenuToggle.click();
+            if (event.which === constants.keyCodes.space) {
+                $dropdownMenuToggle.click();
                 event.preventDefault();
             }
 
             // if escape key pressed
-        if (event.which === keyCodes.escape) {
-            dropdownMenuToggle.click();
+            if (event.which === constants.keyCodes.esc) {
+                $dropdownMenuToggle.click();
                 event.preventDefault();
             }
 
             // if up arrow key pressed or shift+tab else down key or tab is pressed
-        if (event.which === keyCodes.upArrow || event.which === keyCodes.leftArrow ||
-            (event.which === keyCodes.tab && event.shiftKey)) {
+            if (event.which === constants.keyCodes.up || event.which === constants.keyCodes.left ||
+                (event.which === constants.keyCodes.tab && event.shiftKey)) {
                 // if first item go to last
                 if (focusedItemIndex === 0) {
                     menuItems.last().focus();
@@ -77,8 +65,8 @@ $(document).ready(function() {
                     menuItems.get(itemToFocusIndex).focus();
                 }
                 event.preventDefault();
-        } else if (event.which === keyCodes.downArrow || event.which === keyCodes.rightArrow ||
-            event.which === keyCodes.tab) {
+            } else if (event.which === constants.keyCodes.down || event.which === constants.keyCodes.right ||
+                event.which === constants.keyCodes.tab) {
                 // if last item go to first
                 if (focusedItemIndex === numberOfMenuItems - 1) {
                     menuItems.first().focus();
@@ -89,4 +77,11 @@ $(document).ready(function() {
                 event.preventDefault();
             }
         }
-});
+
+        // catch keypresses when inside dropdownMenu
+        // (we want to catch spacebar; escape; up arrow or shift+tab; and down arrow or tab)
+        $dropdownMenu.on('keydown', function(event) {
+            catchKeyPress($(this), event);
+        });
+    });
+}).call(this, require || RequireJS.require);