Functions in JavaScript

Introduction: Link to heading

Functions are reusable blocks of code that perform a specific task. They are an essential tool for writing efficient and organized JavaScript code.

Types of functions Link to heading

  • Declaratives: They are defined using the function keyword.
  • Expression: They are defined as an expression that is assigned to a variable.

Examples Link to heading

Declaratives: Link to heading

// Function declaration
function myFunction() {
    // Function code
    return 3;
// Function call

Expression: Link to heading

// Declaration of the function as an expression
var myFunction = function(a, b) {
    // Function code
    return a + b;
// Function call
myFunction(1, 2);

Getting results Link to heading

  • Browser Console: console.log() can be used to print the value of a variable or expression to the browser console.
  • Return: The function can return a value using the return keyword.

Examples Link to heading

Browser console Link to heading

function greetStudents(student) {

greetStudents("John"); // Print "John" to the console

Return: Link to heading

function add(a, b) {
    var result = a + b;
    return result;

var sum = add(1, 2); // The variable `sum` stores the result of the function, which is 3

More examples: Link to heading

// Function that calculates the area of ​​a square
function squareArea(side) {
return side \* side;

var area = squareArea(5); // The variable `area` stores the area of ​​the square, which is 25

// Function that checks if a number is even
function isEven(number) {
    return number % 2 === 0;

var isEven = isEven(10); // The variable `isEven` stores `true` because 10 is an even number

// Function that greets a user
function greetUser(name) {
return `Hello ${name}, how are you?`;

var greeting = greetUser("Diego"); // The variable `greeting` stores the message "Hello Diego, how are you?"

Tips for using functions: Link to heading

  • Use descriptive names for functions.
  • Break your code into small, manageable functions.
  • Document your features with comments.
  • Reuse functions whenever possible.

Keep learning about functions in JavaScript to improve your programming skills!

Take advantage of understanding functions to write more modular and effective JavaScript code!

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