Javascript Datatypes 2

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Data types (Boolean)

• The boolean type has only two values: true and false.
• This type is commonly used to store yes/no values: true means “yes, correct”, and false means “no, incorrect”.
• Boolean values are mostly gotten from comparisons:

Data types (null)

• The value null represents the intentional absence of a value
• The null type is a special value which represents “nothing”, “empty” or “value unknown”.

• Note that type of null is object for legacy reasons
• An unassigned variable is automatically set to type null
• Use null to assign an “empty” or “unknown” value to a variable

Data types (undefined)

• The value undefined means a value is not assigned
• A declared variable without assigned values becomes undefined by default
• Show example of type of undefined

Data types (object)

• Objects are one of the most important data type in JavaScript
• Objects are used to store keyed collections of data and more complex entities.
• All other types are called “primitive” because their values can contain only a single value
• Objects are associative arrays with several special features. They store properties (key-value pairs), where:
• You can retrieve values using dot notation or with square brackets
• Objects are store any valid JavaScript type including objects themselves
• delete a property: delete obj.prop.