execute only if element is on page

js/burgerMenu.js

-document.querySelector("#burgerMenu").onclick = () => {
-    document.getElementById("burgerMenu").classList.toggle("change");
-    document.getElementById("mainMenuContainer").classList.toggle("visible");
+let burgerMenu = document.querySelector("#burgerMenu");
 
+if(burgerMenu != null) {
+    burgerMenu.onclick = () => {
+        document.getElementById("burgerMenu").classList.toggle("change");
+        document.getElementById("mainMenuContainer").classList.toggle("visible");
+
+    }
 }
\ No newline at end of file

js/cookie.js

@@ -10,15 +10,19 @@ function getCookie(name){
     return null
 }
 
+
 let cookieInfo = document.querySelector(".cookieinfo");
-if (getCookie("cookieMessageHide") === "1"){
-    cookieInfo.style.display = "none";
-} else {
-    cookieInfo.style.display = "block";
-}
+if(cookieInfo != null) {
+    if (getCookie("cookieMessageHide") === "1") {
+        cookieInfo.style.display = "none";
+    } else {
+        cookieInfo.style.display = "block";
+    }
 
-document.querySelector(".cookieinfo-close").onclick = function() {
-    console.log("close");
-    document.cookie = "cookieMessageHide=1";
-    cookieInfo.style.display = "none";
-}
+    document.querySelector(".cookieinfo-close").onclick = function() {
+        console.log("close");
+        document.cookie = "cookieMessageHide=1";
+        cookieInfo.style.display = "none";
+    }
+
+}
\ No newline at end of file