|Gets initialized?||No.||Yes. The
|Members of this data type:||It is the sole member of its own data type.||It is the sole member of its own data type.|
|This returned value means...||no value for numbers, strings, and objects.||no value. It is the value of a variable that has not yet been initialized. It is also the value you get when you query the value of an object property or array element that does not exist.|
- undefined is returned by functions that do not have a return value.
- undefined is the value assigned to function parameters for which no argument is assigned.
|In ECMAScript 3...||
|In ECMAScript 5...||
|Both indicate an absence of value.|
|Equal when compared with the
|The values of each data type evaluate to
|Neither data type has any properties or methods|
|Trying to access a property or method using
|There are no wrapper objects for