An “undefined variable” is different from the value undefined. An undefined variable: var a; alert(b); // ReferenceError: b is not defined A variable with the value undefined: var a; alert(a); // Alerts “undefined” When a function takes an argument, that argument is always declared even if its value is undefined, and so there won’t be … Read more
department is meant to be a string (to be used here as array key). Strings in PHP must be enclosed in quotes. In the days of the long past PHP was lax about using quotes for single-word strings but these days are long gone. Therefore, it must be ‘department’ or “department”. The same goes for … Read more
JQuery library was developed specifically to simplify and to unify certain JavaScript functionality. However if you need to check a variable against undefined value, there is no need to invent any special method, since JavaScript has a typeof operator, which is simple, fast and cross-platform: if (typeof value === “undefined”) { // … } It … Read more
Pointer Dereferencing a NULL pointer Dereferencing a pointer returned by a “new” allocation of size zero Using pointers to objects whose lifetime has ended (for instance, stack allocated objects or deleted objects) Dereferencing a pointer that has not yet been definitely initialized Performing pointer arithmetic that yields a result outside the boundaries (either above or … Read more
Please read “How to Write Go Code”. Use go build or go install within the package directory, or supply an import path for the package. Do not use file arguments for build or install. While you can use file arguments for go run, you should build a package instead, usually with go run ., though … Read more
response[0] is not defined, check if it is defined and then check for its property title. if(typeof response[0] !== ‘undefined’ && typeof response[0].title !== ‘undefined’){ //Do something }
var lastname = “Hi”; if(typeof lastname !== “undefined”) { alert(“Hi. Variable is defined.”); }
Yes, it can do that, but strictly speaking that will assign the default value if the retrieved value is falsey, as opposed to truly undefined. It would therefore not only match undefined but also null, false, 0, NaN, “” (but not “0”). If you want to set to default only if the variable is strictly … Read more
I’m a bit confused about Javascript undefined & null. null generally behaves similarly to other scripting languages’ concepts of the out-of-band ‘null’, ‘nil’ or ‘None’ objects. undefined, on the other hand, is a weird JavaScript quirk. It’s a singleton object that represents out-of-band values, essentially a second similar-but-different null. It comes up: When you call … Read more
You can safely use the typeof operator on undefined variables. If it has been assigned any value, including null, typeof will return something other than undefined. typeof always returns a string. Therefore if (typeof maybeObject != “undefined”) { alert(“GOT THERE”); }