9 files changed, 14 insertions, 13 deletions
diff --git a/js/src/carousel.js b/js/src/carousel.js
index 6bcf470f9..873660519 100644
--- a/js/src/carousel.js
+++ b/js/src/carousel.js
@@ -443,7 +443,7 @@ const Carousel = (($) => {
         if (typeof config === 'number') {
           data.to(config)
         } else if (typeof action === 'string') {
-          if (data[action] === undefined) {
+          if (typeof data[action] === 'undefined') {
             throw new Error(`No method named "${action}"`)
           }
           data[action]()
diff --git a/js/src/collapse.js b/js/src/collapse.js
index 2f00b98cb..718630bd3 100644
--- a/js/src/collapse.js
+++ b/js/src/collapse.js
@@ -343,7 +343,7 @@ const Collapse = (($) => {
         }
 
         if (typeof config === 'string') {
-          if (data[config] === undefined) {
+          if (typeof data[config] === 'undefined') {
             throw new Error(`No method named "${config}"`)
           }
           data[config]()
diff --git a/js/src/dropdown.js b/js/src/dropdown.js
index 5e792a527..e1c48ac6e 100644
--- a/js/src/dropdown.js
+++ b/js/src/dropdown.js
@@ -204,7 +204,7 @@ const Dropdown = (($) => {
 
     _getConfig(config) {
       const elementData = $(this._element).data()
-      if (elementData.placement !== undefined) {
+      if (typeof elementData.placement !== 'undefined') {
         elementData.placement = AttachmentMap[elementData.placement.toUpperCase()]
       }
 
@@ -287,7 +287,7 @@ const Dropdown = (($) => {
         }
 
         if (typeof config === 'string') {
-          if (data[config] === undefined) {
+          if (typeof data[config] === 'undefined') {
             throw new Error(`No method named "${config}"`)
           }
           data[config]()
diff --git a/js/src/modal.js b/js/src/modal.js
index 9f17fafc8..d21a137fb 100644
--- a/js/src/modal.js
+++ b/js/src/modal.js
@@ -507,7 +507,7 @@ const Modal = (($) => {
         }
 
         if (typeof config === 'string') {
-          if (data[config] === undefined) {
+          if (typeof data[config] === 'undefined') {
             throw new Error(`No method named "${config}"`)
           }
           data[config](relatedTarget)
diff --git a/js/src/popover.js b/js/src/popover.js
index 0e8953f77..7639e3e20 100644
--- a/js/src/popover.js
+++ b/js/src/popover.js
@@ -162,7 +162,7 @@ const Popover = (($) => {
         }
 
         if (typeof config === 'string') {
-          if (data[config] === undefined) {
+          if (typeof data[config] === 'undefined') {
             throw new Error(`No method named "${config}"`)
           }
           data[config]()
diff --git a/js/src/scrollspy.js b/js/src/scrollspy.js
index b70b7e477..588f65298 100644
--- a/js/src/scrollspy.js
+++ b/js/src/scrollspy.js
@@ -231,7 +231,7 @@ const ScrollSpy = (($) => {
       for (let i = this._offsets.length; i--;) {
         const isActiveTarget = this._activeTarget !== this._targets[i]
             && scrollTop >= this._offsets[i]
-            && (this._offsets[i + 1] === undefined ||
+            && (typeof this._offsets[i + 1] === 'undefined' ||
                 scrollTop < this._offsets[i + 1])
 
         if (isActiveTarget) {
@@ -246,6 +246,7 @@ const ScrollSpy = (($) => {
       this._clear()
 
       let queries = this._selector.split(',')
+      // eslint-disable-next-line arrow-body-style
       queries     = queries.map((selector) => {
         return `${selector}[data-target="${target}"],` +
                `${selector}[href="${target}"]`
@@ -287,7 +288,7 @@ const ScrollSpy = (($) => {
         }
 
         if (typeof config === 'string') {
-          if (data[config] === undefined) {
+          if (typeof data[config] === 'undefined') {
             throw new Error(`No method named "${config}"`)
           }
           data[config]()
diff --git a/js/src/tab.js b/js/src/tab.js
index 4c3091495..c32cd3776 100644
--- a/js/src/tab.js
+++ b/js/src/tab.js
@@ -238,7 +238,7 @@ const Tab = (($) => {
         }
 
         if (typeof config === 'string') {
-          if (data[config] === undefined) {
+          if (typeof data[config] === 'undefined') {
             throw new Error(`No method named "${config}"`)
           }
           data[config]()
diff --git a/js/src/tooltip.js b/js/src/tooltip.js
index 2060cebbb..721f04481 100644
--- a/js/src/tooltip.js
+++ b/js/src/tooltip.js
@@ -698,7 +698,7 @@ const Tooltip = (($) => {
         }
 
         if (typeof config === 'string') {
-          if (data[config] === undefined) {
+          if (typeof data[config] === 'undefined') {
             throw new Error(`No method named "${config}"`)
           }
           data[config]()
diff --git a/js/src/util.js b/js/src/util.js
index 387c7d2ed..69fb8283c 100644
--- a/js/src/util.js
+++ b/js/src/util.js
@@ -42,7 +42,7 @@ const Util = (($) => {
         if ($(event.target).is(this)) {
           return event.handleObj.handler.apply(this, arguments) // eslint-disable-line prefer-rest-params
         }
-        return undefined
+        return undefined // eslint-disable-line no-undefined
       }
     }
   }
@@ -55,7 +55,7 @@ const Util = (($) => {
     const el = document.createElement('bootstrap')
 
     for (const name in TransitionEndEvent) {
-      if (el.style[name] !== undefined) {
+      if (typeof el.style[name] !== 'undefined') {
         return {
           end: TransitionEndEvent[name]
         }
@@ -138,7 +138,7 @@ const Util = (($) => {
 
     typeCheckConfig(componentName, config, configTypes) {
       for (const property in configTypes) {
-        if (configTypes.hasOwnProperty(property)) {
+        if (Object.prototype.hasOwnProperty.call(configTypes, property)) {
           const expectedTypes = configTypes[property]
           const value         = config[property]
           const valueType     = value && isElement(value) ?