Interesting Facts about JavaScript Functions
Last Updated : 16 Jan, 2025
Let us talk about some interesting facts about JavaScript Functions that can make you an efficient programmer.
Functions Are First-Class Citizens
JavaScript treats functions as first-class citizens, meaning they can be:
- Stored in variables
- Passed as arguments to other functions
- Returned from other functions
This flexibility makes JavaScript functions a powerful tool for functional programming.
JavaScript const greet = () => console.log("Hello, World!"); const sayHi = greet; sayHi(); Functions Can Be Anonymous
JavaScript allows functions without a name, referred to as anonymous functions. These are especially useful in callbacks.
JavaScript setTimeout(function() { console.log("Executed after 2 seconds!"); }, 2000); Closures: Functions Remember Their Scope
Functions in JavaScript form closures, which means they retain access to their lexical scope even when executed outside of it.
JavaScript function createCounter() { let count = 0; return function() { count++; console.log(count); }; } const counter = createCounter(); //Driver Code Starts{ counter(); counter(); //Driver Code Ends } Functions Are Objects
In JavaScript, functions are a special type of object, with properties like name and length. You can also dynamically add properties to functions.
JavaScript function example() {} example.info = "This is a function object"; console.log(example.info); OutputThis is a function object
Default Parameters
JavaScript supports default parameter values, simplifying the creation of functions with optional parameters.
JavaScript function greet(name = "Guest") { console.log(`Hello, ${name}!`); } //Driver Code Starts{ greet(); greet("Meeta"); //Driver Code Ends } OutputHello, Guest! Hello, Meeta!
Arrow Functions Simplify Syntax
Arrow functions provide a concise way to define functions and automatically bind this to their enclosing context.
JavaScript const add = (a, b) => a + b; console.log(add(5, 3));
Functions Can Be Immediately Invoked
JavaScript allows functions to be executed immediately upon definition using an Immediately Invoked Function Expression (IIFE).
JavaScript (function() { console.log("Executed immediately!"); })(); OutputExecuted immediately!
Rest Parameters
Rest parameters allow a function to accept an indefinite number of arguments as an array.
JavaScript function sum(...numbers) { return numbers.reduce((acc, num) => acc + num, 0); } console.log(sum(1, 2, 3, 4)); Functions Can Be Used as Constructors
In JavaScript, functions can be used to create objects using the new keyword.
JavaScript function Person(name) { this.name = name; } const person = new Person("Meeta"); console.log(person.name); Recursive Functions
JavaScript functions can call themselves, enabling recursion for problems like factorials or tree traversals.
JavaScript function factorial(n) { return n <= 1 ? 1 : n * factorial(n - 1); } console.log(factorial(5)); Hoisting of Function Declarations
Function declarations are hoisted, meaning they can be called before they are defined in the code.
JavaScript sayHello(); function sayHello() { console.log("Hello, World!"); } Higher-Order Functions
Functions that take other functions as arguments or return them are called higher-order functions.
JavaScript function calculate(a, b, operation) { return operation(a, b); } console.log(calculate(5, 3, (x, y) => x + y)); Functions Are Dynamic
In JavaScript, you can dynamically modify or assign new functionality to an existing function.
JavaScript function greet() { console.log("Hello!"); } greet(); greet = function() { console.log("Hi there!"); }; greet(); Currying Functions
Currying is a functional programming technique where a function takes one argument at a time and returns another function to handle the next argument.
JavaScript function multiply(a) { return function(b) { return a * b; }; } //Driver Code Starts{ const double = multiply(2); console.log(double(5)); console.log(multiply(3)(4)); //Driver Code Ends } Functions Can Have Their Own Methods
As functions are objects, you can attach methods to them just like you would with objects.
JavaScript function greet() { console.log("Hello!"); } greet.sayHi = function() { console.log("Hi from a method!"); }; //Driver Code Starts{ greet(); greet.sayHi(); //Driver Code Ends } OutputHello! Hi from a method!
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