JavaScript Data Types

JavaScript Data Types

In JavaScript there are 5 different data types that can contain values:

• string
• number
• boolean
• object
• function

There are 6 types of objects:

• Object
• Date
• Array
• String
• Number
• Boolean

And 2 data types that cannot contain values:

• null
• undefined

The typeof Operator

You can use the typeof operator to find the data type of a JavaScript variable.

• typeof "John"                 // Returns "string"
• typeof 3.14                   // Returns "number"
• typeof NaN                    // Returns "number"
• typeof false                  // Returns "boolean"
• typeof [1,2,3,4]              // Returns "object"
• typeof {name:'John', age:34}  // Returns "object"
• typeof new Date()             // Returns "object"
• typeof function () {}         // Returns "function"
• typeof myCar                  // Returns "undefined" *
• typeof null                   // Returns "object"

• 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
• The data type of a variable that has not been assigned a value is also undefined