Data Types

A variable in JavaScript can contain any data.
It is possible to assign a string to a variable initially and then reassign the variable to a number.
A programming language that has this capability is called 'Dynamically Typed'


Data TypeValue or ReferenceComments
stringValue Typeis Immutable and cannot be changed once they have been created
numberValue Typeis Immutable and cannot be changed once they have been created
(float) Prone to rounding errors
bigintValue Type 
booleanValue Type 
symbolValue TypeAdded in ES 2015
nullValue Type 
undefinedValue Type 
   
objectReference Typeis Mutable and can be changed once it has been created
functionReference Typeis Mutable and can be changed once it has been created


function Data Type

A 'function' data type is a special type of object.

typeof function() {} // "function" 
typeof new Function // "function"


array Data Type

An 'array' data type is a special type of object.
It does have some additional properties and functions that a normal object does not have.

typeof myArray            // "object" 

Arrays


null evaluates to False in a boolean expression
undefined evaluates to False in a boolean expression
primitive data types are equal if the values match




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