array in js

Array in JavaScript

Arrays are a type of object in JavaScript that can store multiple values in a single variable. In other words, it is a collection of data items of the same type stored in contiguous memory locations. Each item in an array is called an element and is accessed by its index number.

Creating an Array

To create an array, we can use the array literal notation, which is a comma-separated list of values enclosed in square brackets:

var fruits = ["apple", "banana", "orange"];

We can also create an array using the Array() constructor:

var cars = new Array("BMW", "Mercedes", "Audi");

Note that the Array() constructor can also take a single argument representing the length of the array to be created.

Accessing Array Elements

We can access the elements of an array using their index numbers. The first element has an index of 0, the second element has an index of 1, and so on. We can also use negative index numbers to access elements from the end of the array.

var fruits = ["apple", "banana", "orange"];
console.log(fruits[0]); // Output: "apple"
console.log(fruits[1]); // Output: "banana"
console.log(fruits[2]); // Output: "orange"
console.log(fruits[-1]); // Output: undefined
console.log(fruits[3]); // Output: undefined
console.log(fruits[fruits.length - 1]); // Output: "orange"

Array Methods

JavaScript provides many methods for working with arrays. Some of the commonly used methods are:

• push(): adds one or more elements to the end of an array
• pop(): removes the last element from an array and returns it
• shift(): removes the first element from an array and returns it
• unshift(): adds one or more elements to the beginning of an array
• slice(): returns a new array containing a portion of the original array
• splice(): removes or replaces existing elements and/or adds new elements to an array

Here's an example of using some of these methods:

var fruits = ["apple", "banana", "orange"];
console.log(fruits.length); // Output: 3

fruits.push("grape");
console.log(fruits); // Output: ["apple", "banana", "orange", "grape"]
console.log(fruits.length); // Output: 4

var lastFruit = fruits.pop();
console.log(lastFruit); // Output: "grape"
console.log(fruits); // Output: ["apple", "banana", "orange"]
console.log(fruits.length); // Output: 3

var firstFruit = fruits.shift();
console.log(firstFruit); // Output: "apple"
console.log(fruits); // Output: ["banana", "orange"]
console.log(fruits.length); // Output: 2

fruits.unshift("kiwi", "pear");
console.log(fruits); // Output: ["kiwi", "pear", "banana", "orange"]
console.log(fruits.length); // Output: 4

var citrusFruits = fruits.slice(2);
console.log(citrusFruits); // Output: ["banana", "orange"]
console.log(fruits); // Output: ["kiwi", "pear", "banana", "orange"]

var removedFruits = fruits.splice(1, 2, "cherry", "pineapple");
console.log(removedFruits); // Output: ["pear", "banana"]
console.log(fruits); // Output: ["kiwi", "cherry", "pineapple", "orange"]
console.log(fruits.length); // Output: 4

These are just a few of the many methods available for working with arrays in JavaScript. Knowing how to use them can make your code more efficient and easier to read.