Avoid registering custom elements if already registered

Author: mislav

src/relative-time-element.js

@@ -54,5 +54,7 @@ function updateNowElements() {
 //   var time = new RelativeTimeElement()
 //   # => <relative-time></relative-time>
 //
-window.RelativeTimeElement = RelativeTimeElement
-window.customElements.define('relative-time', RelativeTimeElement)
+if (!window.customElements.get('relative-time')) {
+  window.RelativeTimeElement = RelativeTimeElement
+  window.customElements.define('relative-time', RelativeTimeElement)
+}

src/time-ago-element.js

@@ -14,5 +14,7 @@ export default class TimeAgoElement extends RelativeTimeElement {
   }
 }
 
-window.TimeAgoElement = TimeAgoElement
-window.customElements.define('time-ago', TimeAgoElement)
+if (!window.customElements.get('time-ago')) {
+  window.TimeAgoElement = TimeAgoElement
+  window.customElements.define('time-ago', TimeAgoElement)
+}

src/time-until-element.js

@@ -14,5 +14,7 @@ export default class TimeUntilElement extends RelativeTimeElement {
   }
 }
 
-window.TimeUntilElement = TimeUntilElement
-window.customElements.define('time-until', TimeUntilElement)
+if (!window.customElements.get('time-until')) {
+  window.TimeUntilElement = TimeUntilElement
+  window.customElements.define('time-until', TimeUntilElement)
+}