How to check 'undefined' value in jQuery
javascript, jquery, undefined
Solution
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 returns a string indicating the type of the variable or other unevaluated operand. The main advantage of this method, compared to `if (value === undefined) { ... }`, is that `typeof` will never raise an exception in case if variable `value` does not exist.
Problem
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 == undefined) // do this else // do this } ```