JavaScript : Data Types

What are data types?

The data types are just categorizations of data into different types depending upon various use cases. Javascript categorizes data into two types.

1. Primitive - Immutable values

   • number

   • string

   • boolean

   • bigInt

   • null

   • undefined

   • symbol

2. Object - Anything which is not primitive.

Number

Integers or floating point numbers. In JavaScript, primarily they are defined using Number Literals.

Examples: 123, 12.3

Note: BigInt is an extension of the Number data type with high precision.

String

Text data. In JavaScript, strings are primarily defined using String Literals.

Examples: "Hello" 'Hello'

Boolean

Logical values - True or False also called Boolean Literals. Booleans are usually used in combination with control statements like if-else, for loop, switch etc.

Null and Undefined

These are special values used in different use cases. The most common use case is to use them as a pre-initialized value for a variable.

null indicates the absence of an object value, which could be defined later.

undefined indicates the absence of a primitive value, which could be defined later.

Object

Objects are mutable, unlike primitive values. We define an object in the form of key & value pairs. Each pair is called a property. Where a property key could be any valid JavaScript identifier. A property value could be any valid JavaScript datatype including objects.

Example

{
    key1:"Hello"  //string as value
    key2:123      //number as value
    key3:true     //boolean as value
    key4:{ }      //object as value
}

Property value could be a function also ( in JavaScript functions are callable objects), we call them methods.

{
    firstName:"Subham",                       
    lastName:"Sahu",
    getFullName: function () {                // method
        return this.firstName + this.lastName;
    }    
}

For you to explore.

Learn about,

1. symbol data type.

2. typeof Operator.

What Next?

• What are other ways to define each data type?

• Can we convert one data type to another?