table.isColumnVisible("some") is wrong

https://snippet.webix.com/xc6h0kh9

I try with an example from webix. And it’s working not right. How to fix that issue. It’s make my program error because it’s alway return TRUE althought the column is not visible or not exist

isColumnVisible presumes that column exists and only checks if it is not in hidden list.
to be sure that column is NOT visible, use this

var isHidden = table.getColumnIndex(Id)<0;

again, it does not mean that the column exists.
to check it it exists use getColumnConfig

var colExists = !!table.getColumnConfig(Id);

OK. I am confusing when choose use !! and Boolean function. Which one can i choose ?

hah. I got it. Thank you intregal.