How do you define a function in JavaScript?

Q: How do you define a function in JavaScript?

Function Declaration/definition Function Expression Arrow Function Immediately Invoked Function Expression (IIFE) Generator Function (ES6) Async Function (ES8) Method Definition in Objects Constructor Function Class Method (ES6) function functionName(parameters) { // Function body } const functionName = function(parameters) { // Function body }; const functionName = (parameters) => { // Function body }; (function(parameters) { // Function body })(arguments); function* functionName(parameters) { // Function body with yield statements } async function functionName(parameters) { // Function body with await statements } const obj = { methodName(parameters) { // Function body } }; function Person(name, age) { this.name = name; this.age = age; } const person = new Person('John', 30); console.log(person.name); // Output: John class Calculator { add(a, b) { return a + b; } } const calc = new Calculator(); console.log(calc.add(2, 3)); // Output: 5

Difficulty: 4/10

hoisting, lexical scope, arrow functions

There are many ways in which we can define a function in Javascript depending on scenario and use cases:

1
Function Declaration/definition
2
Function Expression
3
Arrow Function
4
Immediately Invoked Function Expression (IIFE)
5
Generator Function (ES6)
6
Async Function (ES8)
7

Function Declaration: This is the most common and traditional way to define a function.

A function expression defines a function as part of an expression. It can be named or anonymous.

Arrow functions provide a concise syntax for writing functions. They are anonymous and do not have their own this context.

An IIFE is a function that is executed immediately after it is defined.

Generator functions allow you to define an iterative algorithm by using the function* syntax. They can be paused and resumed.

Async functions are used to work with asynchronous code and return a promise. They are defined using the async keyword.

Functions can also be defined as methods within objects.

Constructor functions are used to create objects. They are typically used with the new keyword.

Class Method (ES6): In ES6, you can define functions as methods within a class.

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