– Daniel Schaffer Aug 2, 2010 at 18:09 3 See: How to check for undefined in javascript?, and whether a variable is undefined and How to handle ‘undefined’ in javascript – Shog9 Aug 3, …

I can't find any difference between typeof somevar == 'undefined' and typeof somevar === 'undefined', because typeof always returns string. For null it will return 'object'. Or could be that …

While literally using the keyword undefined, Boolean(undefined) works, trying that with an undefined variable doesn't work, and that is the whole point of doing the check for null or …

Oct 23, 2025 · How do you test if a variable is undefined? Asked 15 years ago Modified 4 days ago Viewed 431k times

Sep 25, 2010 · Using Firefox, working on a Firefox extension, I continually get a javascript warning: reference to undefined property mySidebar.context.netProgress I have tried multiple …

Feb 22, 2011 · The difference between null and undefined is: JavaScript will never set anything to null, that's usually what we do. While we can set variables to undefined, we prefer null …

Apr 22, 2009 · The biggest misconception in many of the answers here is that 'undefined' is a Javascript keyword. It's not a keyword at all, but a variable that (most of the time) happens to …

typeof MyVariable == 'undefined' doesn't discern between an initialized variable with an undefined value and an undeclared variable unless the variable was initially declared and initialized to …

Undefined reference to main - collect2: ld returned 1 exit status Asked 14 years ago Modified 1 year ago Viewed 416k times

Jun 12, 2014 · 5 Technically you should be testing if map is undefined, not map.getCenter(). You can't call a function on an undefined reference.