The array is a data structure that is used to store a large collection of data. Why do we need data structures?
For storing a single data entry we can use one variable like
var friend = "Manish";
Suppose we want to store four friends we might need four variables
var friend1 = "John";
var friend2 = "Raj";
var friend3 = "Harry";
var friend4 = "Zach";
But in large applications like Facebook, where there are a billion users who have billions of friends, posting trillion of texts, posting and commenting. It is difficult to store data using variables.
To deal with huge datasets we use data-structures. The array is mostly used.
Creating an Array
Use the below syntax to create an array
var shoppingList = []; //Empty Array
var country = ["India","USA","Brazil"];
//The array contains similar data and of one type that is string
var clothes = [0, "shirt", 420, true, 1, "jeans", 500, false];
//The array can also contain data of many types.
Retrieve data from an array
The friends' example discussed above can be turned as below
var friends = ["John", "Raj", "Harry", "Zach"];
The name of the friends is stored in the friends
array. We can retrieve the name of the friend Harry
below syntax is used.
console.log(friends[2]); // Output --> Harry
In friends[2]
2 is the index and in an array, the index starts from 0 indexes up to length of Array - 1
.
Mostly Used Built-in Array Methods
- Push - This method is used to add a new element to the end of the array. It updates the array with the new element and returns the new length of the array.
var arrPush = [1,2,3];
arrPush.push("Hello there!");
// returns 4, that is, length of array and arrPush is updated as [1,2,3,"Hello there!"]
- Pop - This method is used to remove the element from the end of the existing array. It updates the array with removing the element an returns the element removed.
var arrPop = [1,"air",3,"water"];
arrPop.pop();
// returns "water", that is, element removed and arrPop is updated as [1,"air",3]
Shift - This method works like pop the difference is it removes the element from the beginning of the array.
Unshift - This method works like push the difference is it adds an element to the beginning of the array.
Slice - The slice method is used to convert the selected elements into a new array object.
var fruits = ["Banana", "Orange", "Apple", "Mango"];
var newFruits = fruits.slice(1,3);
// ["Orange", "Apple"]
//First parameter denotes start selecting of the element
//Second parameter tells to which element we want
console.log(fruits);
// Outputs --> ["Banana", "Orange", "Apple", "Mango"]
- Splice - Splice is a dynamic method that helps in adding/remove items to/from the array.
var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.splice(2, 0, "Lemon", "Kiwi");
console.log(fruits);
//["Banana", "Orange", "Lemon", "Kiwi", "Apple", "Mango"]
//first parameter - index from which elements needs to be add/removed.
//second parameter - This is optional. tells how many elements needs to be removed.
//other parameter - These are the items that needs to be pushed into the array.
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