Function, Objects and Array In JS.

Source: Dev.to

Functions

A function is a block of code that performs a specific task and can be reused. There are three ways to define a function in JavaScript:

1. Function Declaration
2. Function Expression
3. Arrow Function (ES6) – short syntax, commonly used in modern JS.

Examples

// Function Declaration
function greet(name) {
  return "Hello " + name;
}

console.log(greet("Ajmal"));

// Function Expression
const add = function (a, b) {
  return a + b;
};

console.log(add(5, 3));

// Arrow Function
const multiply = (a, b) => a * b;

console.log(multiply(4, 2));

Objects

Objects store data in key‑value pairs and combine state with behavior.

const person = {
  firstName: "John", // Property
  lastName: "Doe",   // Property
  age: 50,           // Property
  fullName: function() { // Method
    return this.firstName + " " + this.lastName;
  }
};

console.log(person.fullName()); // "John Doe"

Arrays

An array in JavaScript is used to store multiple values in a single variable.

Creating an Array

let fruits = ["Apple", "Banana", "Orange"];

Accessing Elements

console.log(fruits[0]); // Apple
console.log(fruits[2]); // Orange

Length

console.log(fruits.length); // 3

Modifying Elements

fruits[1] = "Mango";
console.log(fruits); // ["Apple", "Mango", "Orange"]

Common Array Methods

• push() – add at end

  fruits.push("Grapes");

• pop() – remove from end

  fruits.pop();

• unshift() – add at start

  fruits.unshift("Pineapple");

• shift() – remove from start

  fruits.shift();