Preventing inspect element from client browser(not working on browser for developer)

prevent.js

   window.onload = function() {
     document.addEventListener("contextmenu", function(e){
       e.preventDefault();
     }, false);
     document.addEventListener("keydown", function(e) {
     //document.onkeydown = function(e) {
       // "I" key
       if (e.ctrlKey && e.shiftKey && e.keyCode ==73) {
         disabledEvent(e);
       }
       // "J" key
       if (e.ctrlKey && e.shiftKey && e.keyCode ==74) {
         disabledEvent(e);
       }

       if(e.ctrlKey && e.shiftKey && e.keyCode==67){
         disabledEvent(e);
       }
       // "S" key + macOS
       if (e.keyCode == 83 && (navigator.platform.match("Mac") ? e.metaKey : e.ctrlKey)) {
         disabledEvent(e);
       }
       // "U" key
       if (e.ctrlKey && e.keyCode == 85) {
         disabledEvent(e);
       }
       // "F12" key
       if (event.keyCode == 123) {
         disabledEvent(e);
       }
     }, false);
     
     function disabledEvent(e){
       if (e.stopPropagation){
         e.stopPropagation();
       } else if (window.event){
         window.event.cancelBubble = true;
       }
       e.preventDefault();
       return false;
     }
   };