Prevent duplicate link rel prefetches and prefetching the current page (

#54)

* Prevent duplicate link rel prefetches and prevent prefetching the current page.

Add two checks against the prospective href to prefetch:
1. Has the href already been prefetched?
2. Is the href equal to the current page?

There is not a benefit to duplicate prefetches or prefetching the current page.
If either check is true, return without prefetching the href.

* Remove unnecessary check for duplicate fetches as prefetch cache should already account for this.

* Include query string in the URL comparison (exclude the fragment).

Co-authored-by: nickFalcone <nfalcone@u.rochester.edu>

src/main.js

@@ -70,6 +70,15 @@ function prefetch(e) {
   if (e.target.origin != location.origin) {
     return;
   }
+  /**
+   * Return the given url with no fragment
+   * @param {string} url potentially containing a fragment
+   * @return {string} url without fragment
+   */
+  const removeUrlFragment = (url) => url.split("#")[0];
+  if (removeUrlFragment(window.location.href) === removeUrlFragment(e.target.href)) {
+    return;
+  }
   var l = document.createElement("link");
   l.rel = "prefetch";
   l.href = e.target.href;