"jquery.min.js:2 jQuery.Deferred exception: header.addclass is not a function TypeError: header.addclass is not a function
at HTMLDocument. (
127.0.0.1:5500/app.js:5:10)
at e (
https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4....)
at t (
https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4....) undefined
k.Deferred.exceptionHook @ jquery.min.js:2
t @ jquery.min.js:2
setTimeout (async)
(anonymous) @ jquery.min.js:2
c @ jquery.min.js:2
fireWith @ jquery.min.js:2
fire @ jquery.min.js:2
c @ jquery.min.js:2
fireWith @ jquery.min.js:2
ready @ jquery.min.js:2
B @ jquery.min.js:2
jquery.min.js:2 Uncaught TypeError: header.addclass is not a function
at HTMLDocument. (app.js:5)
at e (jquery.min.js:2)
at t (jquery.min.js:2)
(anonymous) @ app.js:5
e @ jquery.min.js:2
t @ jquery.min.js:2
setTimeout (async)
k.readyException @ jquery.min.js:2
(anonymous) @ jquery.min.js:2
e @ jquery.min.js:2
t @ jquery.min.js:2
setTimeout (async)
(anonymous) @ jquery.min.js:2
c @ jquery.min.js:2
fireWith @ jquery.min.js:2
fire @ jquery.min.js:2
c @ jquery.min.js:2
fireWith @ jquery.min.js:2
t @ jquery.min.js:2
setTimeout (async)
(anonymous) @ jquery.min.js:2
c @ jquery.min.js:2
fireWith @ jquery.min.js:2
fire @ jquery.min.js:2
c @ jquery.min.js:2
fireWith @ jquery.min.js:2
ready @ jquery.min.js:2
B @ jquery.min.js:2
(index):1 Unchecked runtime.lastError: The message port closed before a response was received."
https://codepen.io/vladimir-iwanow/pen/PowQzjo 
