4. Java Script variable (untype)

No block-level scopes

Data type

There are 5 simple data types (also known as basic data types) in javascript: Undefined, Null, Boolean, number, and string. There are 1 more complex data types--object,object essentially consist of a set of unordered name-value pairs.

typeof operator

While JavaScript is loosely typed, there needs to be a means to detect the data type of a given variable--typeof is the operator that is responsible for the provider aspect information. Using the typeof operator on a value may return one of the following strings:

"Undefined"--if this value is undefined;

"Boolean"--if this value is a Boolean value;

"String"--if the value is a string;

"Number"--if the value is numeric;

"Object"--if this value is an object or null;

"Function"--if the value is a function;

4. Java Script variable (untype)