– 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, …

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 …

May 7, 2009 · Yes, variables can have a value of undefined and you can explicitly assign values to them. Assigning undefined to a variable though is probably confusing, since it's a bit of a …

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 …

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 …

Jan 18, 2011 · 390 The jQuery Core Style Guidelines suggest two different ways to check whether a variable is defined. Global Variables: typeof variable === "undefined" Local Variables: …

Feb 24, 2011 · How do I check a variable if it's null or undefined and what is the difference between the null and undefined? What is the difference between == and === (it's hard to …

Dec 4, 2016 · But check the question: "How to determine if a variable is undefined or null", the ! operand used with an if will always return to true if the variable is null or undefined.

Aug 26, 2008 · How do I check if an object property in JavaScript is undefined?