JS stop code sniffing

It’s not 100% safe. But can protect code for some extent from copycat users.

window.onkeydown = function(e) {
    if(e.keyCode == 123) {
     return false;
    }
    if(e.ctrlKey && e.shiftKey && e.keyCode == 'I'.charCodeAt(0)){
     return false;
    }
    if(e.ctrlKey && e.shiftKey && e.keyCode == 'J'.charCodeAt(0)){
     return false;
    }
    if(e.ctrlKey && e.keyCode == 'U'.charCodeAt(0)){
     return false;
    }

    if(e.ctrlKey && e.shiftKey && e.keyCode == 'C'.charCodeAt(0)){
     return false;
    }      
 }