http://www.bing.com:80/search?q=Undefined+Point+On+GraphSearch resultshttp://www.bing.com:80/s/a/rsslogo.gifhttp://www.bing.com:80/search?q=Undefined+Point+On+GraphCopyright © 2026 Microsoft. All rights reserved. These XML results may not be used, reproduced or transmitted in any manner or for any purpose other than rendering Bing results within an RSS aggregator for your personal, non-commercial use. Any other use of these results requires express written permission from Microsoft Corporation. By accessing this web page or using these results in any manner whatsoever, you agree to be bound by the foregoing restrictions.https://stackoverflow.com/questions/3390396/how-can-i-check-for-undefined-in-javascriptIf it is undefined, it will not be equal to a string that contains the characters "undefined", as the string is not undefined. You can check the type of the variable:Fri, 03 Apr 2026 00:29:00 GMThttps://stackoverflow.com/questions/5076944/what-is-the-difference-between-null-and-undefined-in-javascriptAs typeof returns undefined, undefined is a type where as null is an initializer indicates the variable points to no object (virtually everything in Javascript is an object).Fri, 03 Apr 2026 01:41:00 GMThttps://stackoverflow.com/questions/776950/javascript-undefined-undefinedThe 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 be undefined. So the only time "somevar === undefined" works is when the 'undefined' variable really hasn't been defined.Thu, 02 Apr 2026 14:00:00 GMThttps://stackoverflow.com/questions/2559318/how-can-i-check-for-an-undefined-or-null-variable-in-javascriptWhile 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 undefined.Fri, 03 Apr 2026 00:15:00 GMThttps://stackoverflow.com/questions/833661/what-is-the-difference-in-javascript-between-undefined-and-not-definedAssigning undefined to a variable though is probably confusing, since it's a bit of a paradox (you've defined the variable as undefined) and it's not possible to distinguish that variable from either variables that don't exist or uninitialised variables.Thu, 02 Apr 2026 21:09:00 GMThttps://stackoverflow.com/questions/20624566/understanding-undefined-in-javascript-how-it-works-how-to-safely-check-againThere are 3 undefined in javascript. The global variable undefined, the value undefined and the type undefined. Even if the global variable undefined is overridden, the value undefined still exists. There are several ways to get it one of which is an empty argument to a function, another is a variable declaration without assigning anything:Sun, 29 Mar 2026 15:23:00 GMThttps://stackoverflow.com/questions/5101948/javascript-checking-for-null-vs-undefined-and-difference-between-andHow 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 search Google for "===" )?Fri, 03 Apr 2026 13:30:00 GMThttps://stackoverflow.com/questions/1984721/how-to-handle-undefined-in-javascripttypeof foo !== 'undefined' window.foo !== undefined 'foo' in window The first two should be equivalent (as long as foo isn't shadowed by a local variable), whereas the last one will return true if the global varible is defined, but not initialized (or explicitly set to undefined).Mon, 30 Mar 2026 21:05:00 GMThttps://stackoverflow.com/questions/2703102/the-difference-between-typeof-x-undefined-and-x-nullI 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 I am wrong?Sun, 29 Mar 2026 05:58:00 GMThttps://stackoverflow.com/questions/7231873/javascript-undefined-conditionundefined is a variable, not a constant, and can be assigned a value. Because of this, one school of thought says the second path is safer, since you cannot be sure of the value of undefined. There is another school of thought that says those who redefine undefined deserve exactly what they get.Tue, 31 Mar 2026 09:01:00 GMT