Javascript example Tutorial: typeof Operator

Since ECMAScript is loose, there is a need to detect the Data Type of a given variable-typeof is the operator responsible for providing this convenient information. Using the typeof operator for a value may return one of the following strings:

"Undefined" -- if this value is not defined

"Boolean" -- if this value is a boolean Value

"String" -- if the value is a string

"Number" -- if this value is a numerical value

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

"Function" -- if this value is a function

Below are several examples of using the typeof OPERATOR:

Var message = "some string ";

Alert (typeof message); // "string"

Alert (typeof (message); // "string"

Alert (typeof 95); // "number"

These examples show that the operand of the typeof operator can be a message or a numeric literal. Note that typeof is an operator rather than a function, so parentheses in the example are not required (although they can be used ).