How to detect Reference Errors in Javascript where Undefined doesn't work?

Question

typeof(nonexistingobj)

returns 'undefined' BUT

typeof(nonexistingobj.nonexistentproperty) 

does not generate 'undefined' as I was expecting, but something called a Reference Error - how do I detect this?

I'm trying to do sub-property detection on the response from an API. (Specifically, the API returns a sub object called data.paging.next when there's another page of API results to get, but no 'next' sub object if it just returned the last page).

Answer 1

Don't try to access a property of undefined . Test if the variable you are trying to access is defined first.

if (typeof obj !== "undefined") {
    typeof obj.nonexistentproperty;
} 

Answer 2

To catch errors you can use try/catch:

try {
     console.log(typeof nonexistingobj.nonexistentproperty);
} catch (error) {
     console.log('Message error: ' + error.message);
}