Switch to strings constants.

This allows the minifier to mangle the constants. It also allows the linter to find unused strings properly.

While at it, remove a few unused properties.

File                        Before      After       Diff
--------------------------------------------------------
bootstrap.bundle.min.js     23.61 kB    22.61 kB    -1.00 kB (-4.23 %)
bootstrap.min.js            17.04 kB    16.08 kB    -0.96 kB (-5.63 %)

1 files changed, 10 insertions, 14 deletions

diff --git a/js/src/popover.js b/js/src/popover.js
index d71a78236c..2d423f0dd5 100644
--- a/js/src/popover.js
+++ b/js/src/popover.js
@@ -39,16 +39,6 @@ const DefaultType = {
   content: '(string|element|function)'
 }
 
-const ClassName = {
-  FADE: 'fade',
-  SHOW: 'show'
-}
-
-const Selector = {
-  TITLE: '.popover-header',
-  CONTENT: '.popover-body'
-}
-
 const Event = {
   HIDE: `hide${EVENT_KEY}`,
   HIDDEN: `hidden${EVENT_KEY}`,
@@ -62,6 +52,12 @@ const Event = {
   MOUSELEAVE: `mouseleave${EVENT_KEY}`
 }
 
+const CLASS_NAME_FADE = 'fade'
+const CLASS_NAME_SHOW = 'show'
+
+const SELECTOR_TITLE = '.popover-header'
+const SELECTOR_CONTENT = '.popover-body'
+
 /**
  * ------------------------------------------------------------------------
  * Class Definition
@@ -109,16 +105,16 @@ class Popover extends Tooltip {
     const tip = this.getTipElement()
 
     // we use append for html objects to maintain js events
-    this.setElementContent(SelectorEngine.findOne(Selector.TITLE, tip), this.getTitle())
+    this.setElementContent(SelectorEngine.findOne(SELECTOR_TITLE, tip), this.getTitle())
     let content = this._getContent()
     if (typeof content === 'function') {
       content = content.call(this.element)
     }
 
-    this.setElementContent(SelectorEngine.findOne(Selector.CONTENT, tip), content)
+    this.setElementContent(SelectorEngine.findOne(SELECTOR_CONTENT, tip), content)
 
-    tip.classList.remove(ClassName.FADE)
-    tip.classList.remove(ClassName.SHOW)
+    tip.classList.remove(CLASS_NAME_FADE)
+    tip.classList.remove(CLASS_NAME_SHOW)
   }
 
   _addAttachmentClass(attachment) {