JavaScript Data Types

JavaScript includes data types similar to other programming languages like Java or C#. JavaScript is dynamic and loosely typed language. It means you don't require to specify a type of a variable. A variable in JavaScript can be assigned any type of value, as shown in the following example.

Example: Loosely Typed Variables
var myvariable = 1;  // numeric value

myvariable = 'one'; // string value

myvariable = 1.1; // decimal value

myvariable = true; // Boolean value

myvariable = null; // null value

In the above example, different types of values are assigned to the same variable to demonstrate loosely typed characteristics of JavaScript. Different values 1, 'one', 1.1, true are examples of different data types.

JavaScript includes primitive and non-primitive data types as per latest ECMAScript 5.1.

Primitive Data Types

The primitive data types are the lowest level of the data value in JavaScript. The typeof operator can be used with primitive data types to know the type of a value.

The followings are primitive data types in JavaScript:

Data Type Description
String String is a textual content wrapped inside ' ' or " " or ` ` (tick sign).

Example: 'Hello World!', "This is a string", etc.
Number Number is a numeric value.

Example: 100, 4521983, etc.
BigInt BigInt is a numeric value in the arbitrary precision format.

Example: 453889879865131n, 200n, etc.
Boolean Boolean is a logical data type that has only two values, true or false.
Null A null value denotes an absense of value.

Example: var str = null;
Undefined undefined is the default value of a variable that has not been assigned any value.

Example: In the variable declaration, var str;, there is no value assigned to str. So, the type of str can be check using typeof(str) which will return undefined.

Structural Data Types

The structural data types contain some kind of structure with primitive data.

Data Type Description
Object An object holds multiple values in terms of properties and methods.

Example:
var person = { 
                firstName: "James", 
                lastName: "Bond", 
                age: 15
            }; 
Date Date object represents date & time including days, months, years, hours, minutes, seconds and milliseconds.

Example: var today = new Date("25 July 2021");
Array An array stores multiple values using special syntax.

Example: var nums = [1, 2, 3, 4];

Learn about each data type in detail in the next section.

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