rewrite get parameter function

js/viewPost.js

@@ -2,18 +2,12 @@ if(window.location['pathname'] == "/post.html"){
     loadPost();
 }
 
-
-function getParameter(key) {
-
-    // Address of the current window
-    let address = window.location.search
-
-    // Returns a URLSearchParams object instance
-    let parameterList = new URLSearchParams(address)
-
-    // Returning the respected value associated
-    // with the provided key
-    return parameterList.get(key)
+// return the value of the get parameter with the given name
+function getParameter(name) {
+    name = name.replace(/[\[]/, "\\[").replace(/[\]]/, "\\]");
+    var regex = new RegExp("[\\?&]" + name + "=([^&#]*)");
+    var results = regex.exec(location.search);
+    return results === null ? "" : decodeURIComponent(results[1].replace(/\+/g, " "));
 }
 
 async function loadPost() {