JavaScript is a dynamically typed language, which means that you do not need to declare the data type of a variable before assigning it a value. The JavaScript engine will automatically determine the data type based on the value that is assigned.
There are seven primitive data types in JavaScript:
Number: Any numeric value, such as 10, 3.14, or -5.67
String: A sequence of characters, such as “Hello, world!” or ‘This is a string.’
Boolean: A logical value, either true or false
Null: A special value that represents the absence of a value
Undefined: A special value that represents a variable that has not yet been assigned a value
BigInt: A new data type (ES2020) that can be used to store integer values that are too big to be represented by a normal JavaScript Number
Symbol: A unique identifier that can be used to add unique property keys to an object
There is also one non-primitive data type:
Object: A collection of properties and values
Primitive Data Types
Primitive data types are stored in the call stack, which is a region of memory that is used to store function calls. Primitive data types are immutable, which means that they cannot be changed once they are created.
Number
The Number data type can represent both integers and floating-point numbers. JavaScript numbers are stored in a 64-bit floating-point format, which means that they can represent a very wide range of values.
Examples
const number1 = 10;
const number2 = 3.14;
const number3 = -5.67;
String
The String data type represents a sequence of characters. Strings can be created using single quotes (‘) or double quotes (“).
Examples
const string1 = "Hello, world!";
const string2 = 'This is a string.';
Boolean
The Boolean data type represents a logical value, either true or false.
Examples
const boolean1 = true;
const boolean2 = false;
Null
The Null data type represents the absence of a value.
Examples
const nullValue = null;
Undefined
The Undefined data type represents a variable that has not yet been assigned a value.
Examples
let undefinedVariable;
BigInt
The BigInt data type (ES2020) can be used to store integer values that are too big to be represented by a normal JavaScript Number.
Examples
const bigInt1 = 900719925124740999n;
const bigInt2 = 1n;
Symbol
The Symbol data type (ES2015) can be used to create unique identifiers that can be used as property keys on objects.
Examples
const symbol1 = Symbol('hello');
const symbol2 = Symbol('hello');
Object Data Type
The Object data type is the only non-primitive data type in JavaScript. Objects are used to store collections of properties and values.
Examples
const object1 = {
name: "John Doe",
age: 30,
occupation: "Software Engineer"
};
const object2 = new Object();
Objects can also be used to represent more complex data structures, such as arrays, lists, and trees.
Data Type Conversion
JavaScript provides a number of functions for converting data types. For example, the parseInt() function can be used to convert a string to a number, and the toString() function can be used to convert a number to a string.
Examples
const numberString = "10";
const number = parseInt(numberString);
const age = 30;
const ageString = age.toString();
Conclusion
JavaScript data types are an important part of the language. By understanding the different data types and how to use them, you can write more efficient and effective JavaScript code.