Improve JS code style.

assets/js/_commons/copy-link.js

@@ -1,13 +1,16 @@
 /*
-* Copy current page url to clipboard.
-* v2.1
-* https://github.com/cotes2020/jekyll-theme-chirpy
-* © 2020 Cotes Chung
-* MIT License
-*/
+ * Copy current page url to clipboard.
+ * v2.1
+ * https://github.com/cotes2020/jekyll-theme-chirpy
+ * © 2020 Cotes Chung
+ * MIT License
+ */
 
 function copyLink(url) {
-  if (!url || 0 === url.length)
+  if (!url || 0 === url.length) {
+    return;
+  }
+
   url = window.location.href;
   var $temp = $("<input>");
 
@@ -17,4 +20,5 @@ function copyLink(url) {
   $temp.remove();
 
   alert("Link copied successfully!");
+
 }