Arrow functions in JavaScript

Arrow functions in JavaScript are a concise way to write functions using the => syntax, automatically binding this from the surrounding context.

The following code defines an arrow function that takes two numbers and returns their sum.

const add = (a, b) => a + b; console.log(add(5, 3)); 

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Syntax:

const functionName = (parameters) => { // function body return result;};

In the above syntax:

• const: declares the function as a constant variable.
• functionName: name of the arrow function.
• (parameters): inputs to the function.
• =>: arrow showing it’s an arrow function (replaces function keyword).
• { ... }: function body where code runs.
• return result; : explicitly returns a value.

1. Arrow Function without Parameters

An arrow function without parameters is defined using empty parentheses (). This type of function is useful when no input values are needed, such as for callbacks, timers, or simple operations.

const gfg = () => {  console.log( "Hi from GeekforGeeks!" ); } gfg(); 

Hi from GeekforGeeks! 

2. Arrow Function with Single Parameters

When an arrow function has only one parameter, parentheses around the parameter can be omitted, making the syntax shorter and cleaner. This is commonly used in callbacks, array methods, or simple operations.

const square = x => x*x; console.log(square(4)); 

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3. Arrow Function with Multiple Parameters

Arrow functions with multiple parameters, like (param1, param2) => { }, simplify writing concise function expressions in JavaScript, useful for functions requiring more than one argument.

const gfg = ( x, y, z ) => {  console.log( x + y + z ) } gfg( 10, 20, 30 ); 

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4. Arrow Function with Default Parameters

Arrow functions support default parameters, allowing predefined values if no argument is passed, making JavaScript function definitions more flexible and concise.

const gfg = ( x, y, z = 30 ) => {  console.log( x + " " + y + " " + z); } gfg( 10, 20 ); 

10 20 30 

5. Return Object Literals

In JavaScript, returning object literals within functions is concise: () => ({ key: value }) returns an object { key: value }, useful for immediate object creation and returning.

const makePerson = (firstName, lastName) => ({first: firstName, last: lastName}); console.log(makePerson("Pankaj", "Bind")); 

{ first: 'Pankaj', last: 'Bind' } 

Async Arrow Functions

Arrow functions can be made asynchronous by adding the async keyword before the parameter list. This allows the function to use the await keyword inside its body to pause execution until a Promise is resolved, making asynchronous code easier to read and manage.

const fetchData = async () => {  const data = await fetch('https://api.example.com/data');  return data.json(); }; 

In this example:

• The async keyword marks the function as asynchronous.
• await can be used inside the function to wait for Promises.
• Returns a Promise automatically.
• Useful for handling API calls, timers, or any asynchronous operations.

Arrow Functions vs. Regular Functions

Here is the detailed Comparsion between Arrow Functions and Regular Functions: