- Datatypes and variables
- Datatypes overview
- Variables declaration
- array as object -> properties and methods
- Anonymous arrays
- associative arrays/hashtables
- Default values for parameters and variable length parameter lists
- return values
- callback functions
- anonymous functions
- Class definition, object initialisation, singletons
- Prototyping concept and inheritance
- Anonymous objects
- Objects as associative arrays
Null means variable has no value at all. Do not confuse null with 0 (zero)! 0 is just a number, null means just no value or a empty or non-existent reference.
A value that is undefined is a value held by a variable right after it has been created and before a value has been assigned to it.