The typeof operator returns the type of a variable, object, function, or expression.

For example:

• The data type of NaN is number
• The data type of an array is object
• The data type of a date is object
• The data type of null is object
• The data type of an undefined variable is undefined

typeof 'Hello World'            // returns string
typeof 66                       // returns number
typeof NaN                      // returns number
typeof true                     // returns boolean
typeof ['apple', 'pear']        // returns object
typeof {name:'Johnny', age:9}   // returns object
typeof new Date()               // returns object
typeof function () {}           // returns function
typeof my_cars                  // returns undefined (since not yet declared)
typeof null                     // returns object