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Possible Duplicate: Detecting an undefined object property in JavaScript javascript undefined compare How we can add a check for an undefined variable, like: function A(val) { if (val ==...
It’s difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For...
I’m trying to write a basic go program that calls a function on a different file, but a part of the same package. However, it returns: undefined: NewEmployee Here...
I’m checking if(response...
This question already has answers here: JavaScript check if variable exists (is defined/initialized) (31 answers) Closed 6 years ago. Things I’ve tried that don’t seem to work: if(lastName !=...
I know that I can test for a JavaScript variable and then define it if it is undefined, but is there not some way of saying var setVariable =...
I’m a bit confused about JavaScript’s undefined and null values. What does if (!testvar) actually do? Does it test for undefined and null or just undefined? Once a variable...
How do I verify the existence of an object in JavaScript? The following works: if (!null) alert("GOT HERE"); But this throws an Error: if (!maybeObject) alert("GOT HERE"); The Error:...
The jQuery Core Style Guidelines suggest two different ways to check whether a variable is defined. Global Variables: typeof variable === "undefined" Local Variables: variable === undefined Properties: object.prop...
Which method of checking if a variable has been initialized is better/correct? (Assuming the variable could hold anything (string, int, object, function, etc.)) if (elem) { // or !elem...