("#panel").is is not a function error Jquery

Question

Ive no idea why this throws back an error

        if((("#panel").is(':visible') && elm.length==0)||((("#panel").is(':hidden') && elm.length>0))){
            showSubMenu()
        }

("#panel").is is not a function ???

Could someone explain to me the logic of why this causes an error ? so that I dont repeat ?

Answer 1

"#panel" is a string.
Strings have no .is() method.

You probably want to call $ to make a jQuery object.