How can I compare a non-existing JavaScript object to undefined without getting a Reference Error?
javascript, referenceerror
Solution
Use this:
(typeof task === "undefined")
When you use `(task === undefined)`, Javascript needs to find the value of `task` to see if it is the same as `undefined`, but it can't look up the name because it doesn't exist, giving you the reference error. `typeof` is special in that it can safely return the type of a name that doesn't exist.
Problem
I want to boolean to come out of this expression ``` (task === undefined); ``` where `task` is arbitrary and doesn’t appear in the code at all. However, when I run this in rhino, I get a reference Error. I WANT TRUE Why don’t I get true? I want to check if a particular variable has been defined. How do I do it then if this doesn't work?