null
JavaScript null type.
Description
JavaScript has the null type built-in as a literal value, and is often used to represent the absence of data. null and undefined are similar in this regard, but null typically shows that a value has been assigned, even if it is empty.
A detailed description of null is available on the Mozilla Developer Network.
Use in DataTables
Where a parameter is shown as accepting a null value, or a method returning a null value, it indicates that a literal null is expected / returned (not to be confused with undefined or false which are different values).