5 files changed, 28 insertions, 17 deletions
diff --git a/js/src/carousel.js b/js/src/carousel.js
index 34cab4391..f990c699a 100644
--- a/js/src/carousel.js
+++ b/js/src/carousel.js
@@ -24,6 +24,8 @@ const Carousel = (($) => {
   const DATA_API_KEY        = '.data-api'
   const JQUERY_NO_CONFLICT  = $.fn[NAME]
   const TRANSITION_DURATION = 600
+  const ARROW_LEFT_KEYCODE  = 37 // KeyboardEvent.which value for left arrow key
+  const ARROW_RIGHT_KEYCODE = 39 // KeyboardEvent.which value for right arrow key
 
   const Default = {
     interval : 5000,
@@ -236,8 +238,8 @@ const Carousel = (($) => {
       }
 
       switch (event.which) {
-        case 37: this.prev(); break
-        case 39: this.next(); break
+        case ARROW_LEFT_KEYCODE: this.prev(); break
+        case ARROW_RIGHT_KEYCODE: this.next(); break
         default: return
       }
     }
diff --git a/js/src/dropdown.js b/js/src/dropdown.js
index 92f841bc4..b2da8f4e4 100644
--- a/js/src/dropdown.js
+++ b/js/src/dropdown.js
@@ -17,12 +17,16 @@ const Dropdown = (($) => {
    * ------------------------------------------------------------------------
    */
 
-  const NAME                = 'dropdown'
-  const VERSION             = '4.0.0-alpha.2'
-  const DATA_KEY            = 'bs.dropdown'
-  const EVENT_KEY           = `.${DATA_KEY}`
-  const DATA_API_KEY        = '.data-api'
-  const JQUERY_NO_CONFLICT  = $.fn[NAME]
+  const NAME                     = 'dropdown'
+  const VERSION                  = '4.0.0-alpha.2'
+  const DATA_KEY                 = 'bs.dropdown'
+  const EVENT_KEY                = `.${DATA_KEY}`
+  const DATA_API_KEY             = '.data-api'
+  const JQUERY_NO_CONFLICT       = $.fn[NAME]
+  const ESCAPE_KEYCODE           = 27 // KeyboardEvent.which value for Escape (Esc) key
+  const ARROW_UP_KEYCODE         = 38 // KeyboardEvent.which value for up arrow key
+  const ARROW_DOWN_KEYCODE       = 40 // KeyboardEvent.which value for down arrow key
+  const RIGHT_MOUSE_BUTTON_WHICH = 3 // MouseEvent.which value for the right button (assuming a right-handed mouse)
 
   const Event = {
     HIDE             : `hide${EVENT_KEY}`,
@@ -152,7 +156,7 @@ const Dropdown = (($) => {
     }
 
     static _clearMenus(event) {
-      if (event && event.which === 3) {
+      if (event && event.which === RIGHT_MOUSE_BUTTON_WHICH) {
         return
       }
 
@@ -218,10 +222,10 @@ const Dropdown = (($) => {
       let parent   = Dropdown._getParentFromElement(this)
       let isActive = $(parent).hasClass(ClassName.OPEN)
 
-      if ((!isActive && event.which !== 27) ||
-           (isActive && event.which === 27)) {
+      if ((!isActive && event.which !== ESCAPE_KEYCODE) ||
+           (isActive && event.which === ESCAPE_KEYCODE)) {
 
-        if (event.which === 27) {
+        if (event.which === ESCAPE_KEYCODE) {
           let toggle = $(parent).find(Selector.DATA_TOGGLE)[0]
           $(toggle).trigger('focus')
         }
@@ -242,11 +246,11 @@ const Dropdown = (($) => {
 
       let index = items.indexOf(event.target)
 
-      if (event.which === 38 && index > 0) { // up
+      if (event.which === ARROW_UP_KEYCODE && index > 0) { // up
         index--
       }
 
-      if (event.which === 40 && index < items.length - 1) { // down
+      if (event.which === ARROW_DOWN_KEYCODE && index < items.length - 1) { // down
         index++
       }
 
diff --git a/js/src/modal.js b/js/src/modal.js
index 695ac569b..bf0a7608f 100644
--- a/js/src/modal.js
+++ b/js/src/modal.js
@@ -25,6 +25,7 @@ const Modal = (($) => {
   const JQUERY_NO_CONFLICT           = $.fn[NAME]
   const TRANSITION_DURATION          = 300
   const BACKDROP_TRANSITION_DURATION = 150
+  const ESCAPE_KEYCODE               = 27 // KeyboardEvent.which value for Escape (Esc) key
 
   const Default = {
     backdrop : true,
@@ -271,7 +272,7 @@ const Modal = (($) => {
     _setEscapeEvent() {
       if (this._isShown && this._config.keyboard) {
         $(this._element).on(Event.KEYDOWN_DISMISS, (event) => {
-          if (event.which === 27) {
+          if (event.which === ESCAPE_KEYCODE) {
             this.hide()
           }
         })
@@ -400,7 +401,7 @@ const Modal = (($) => {
       }
 
       if (this._isBodyOverflowing && !isModalOverflowing) {
-        this._element.style.paddingRight = `${this._scrollbarWidth}px~`
+        this._element.style.paddingRight = `${this._scrollbarWidth}px`
       }
     }
 
diff --git a/js/src/scrollspy.js b/js/src/scrollspy.js
index b9186db00..001f7f56c 100644
--- a/js/src/scrollspy.js
+++ b/js/src/scrollspy.js
@@ -140,6 +140,7 @@ const ScrollSpy = (($) => {
               targetSelector
             ]
           }
+          return null
         })
         .filter((item)  => item)
         .sort((a, b)    => a[0] - b[0])
diff --git a/js/src/util.js b/js/src/util.js
index dba6e9bd6..b779c448f 100644
--- a/js/src/util.js
+++ b/js/src/util.js
@@ -16,6 +16,8 @@ const Util = (($) => {
 
   let transition = false
 
+  const MAX_UID = 1000000
+
   const TransitionEndEvent = {
     WebkitTransition : 'webkitTransitionEnd',
     MozTransition    : 'transitionend',
@@ -40,6 +42,7 @@ const Util = (($) => {
         if ($(event.target).is(this)) {
           return event.handleObj.handler.apply(this, arguments)
         }
+        return undefined
       }
     }
   }
@@ -100,7 +103,7 @@ const Util = (($) => {
     getUID(prefix) {
       do {
         /* eslint-disable no-bitwise */
-        prefix += ~~(Math.random() * 1000000) // "~~" acts like a faster Math.floor() here
+        prefix += ~~(Math.random() * MAX_UID) // "~~" acts like a faster Math.floor() here
         /* eslint-enable no-bitwise */
       } while (document.getElementById(prefix))
       return prefix