Javascript undefined type.


Javascript uses its undefined data type to indicate that no value has been assigned / returned to a parameter or from a function. undefined and null are similar, but null shows that a value has been assigned, even if it is empty.

A detailed description of undefined is available on the Mozilla Developer Network.

Use in DataTables

Where a parameter is shown as accepting a undefined value, or a method returning a undefined value, it indicates that undefined is expected / returned (not to be confused with null or false which are different values).