Deleting a function/variable

// Declear `myfunc` and  `myvar`
window.myfunc=function(a,b){return a+b;};
window.myvar=999;

// Delete `myfunc` and `myvar`
delete myfunc;
delete myvar;

# Inquire `myfunc` and `myvar` in console

>myfunc
VM370:1 Uncaught ReferenceError: myfunc is not defined
    at :1:1
(anonymous) @ VM370:1Understand this error

>myvar
VM387:1 Uncaught ReferenceError: myvar is not defined
    at :1:1