Javascript Array
Arrays store multiple values in the form of a list. The Items in the list can be accessed using index or position. unlike variable where a value of particular data item can be stored in the array. We can store multiple items which belong to different data types.
Creating Arrays
To create an empty array use `array()` method and assign it to a variable.
var fruits = new Array(); //array created with empty items fruits //Console output []
If you click on arrow mark you can see `length:0` which means that there are zero items below will be explained in detail.
Then below length, there is `__proto__` which has a number of methods which can be performed on array `fruits`.
We’ll be covering Array Methods in the next tutorial.
`Array()` can be declared in a shorthand way using square brackets `[]`.The below method gives the same output like the above.
var fruits = []; //array created with empty items fruits //Console output []
Inserting Items in Array
Unlike another statically typed programming language, we can insert items of Different DataTypes in JavaScript Arrays.
Let us create a `cars` array and insert some items.
var cars = []; cars[0]="BMW"; cars[1]="AUDI"; cars[2]="BENZ"; cars[3]="TATA"; console.log(cars); //Console output (4) ["BMW", "AUDI", "BENZ", "TATA"]
In index cars[0] items “BMW” is a store and similarly, other items are stored in their respective index.
Now let us create the same cars array in a single line of code.
var cars = ["BMW", "AUDI", "BENZ", "TATA"]; console.log(cars); //Console output (4) ["BMW", "AUDI", "BENZ", "TATA"]
Inserting items using `push()` method
var cars = ["BMW", "AUDI", "BENZ", "TATA"]; console.log("Before Inserting new item : ",cars); cars.push("VOLVO"); console.log("After Inserting new item : ",cars); //Console output Before Inserting new item : (4) ["BMW", "AUDI", "BENZ", "TATA"] After Inserting new item : (5) ["BMW", "AUDI", "BENZ", "TATA", "VOLVO"]
We can also insert multiple items to an array.
var cars = ["BMW", "AUDI", "BENZ", "TATA"]; cars.push("VOLVO", "FIAT", "MARUTI"); console.log(cars); //Console output (7) ["BMW", "AUDI", "BENZ", "TATA", "VOLVO", "FIAT", "MARUTI"]
Accessing Array Items
Array items can be accessed through indexes.
var cars = ["BMW", "AUDI", "BENZ", "TATA"]; console.log(cars[1]); //Console output AUDI
Check if Item Exists in Array
At the start, we have told you about `length` key in array. This is created with array itself and the value of length changes as we add/remove items in the array.
var cars = ["BMW", "AUDI", "BENZ", "TATA"]; console.log(cars.length); //Console output 4
Check it item exists using if conditional statement
var numbers = [1,2,3,4]; if(numbers.length>0){ console.log("Item exists in array"); }else{ console.log("Item does not exists in array"); } //Console output Item exists in array
Updating Items in Array
We can update a specific item in an array using indexes.
var names = ["John", "Rahul", "Karan"]; names[1]="Rahul Kumar"; console.log(names); //Console output (3) ["John", "Rahul Kumar", "Karan"]
Delete/Remove array items
To remove the item from the array we use `delete` keyword before specifying the array with index.
var names = ["John", "Rahul", "Karan"]; console.log("Before deleting item ",names); delete names[1]; console.log("After deleting item of index 1 ",names); //Console output Before deleting item (3) ["John", "Rahul", "Karan"] After deleting item of index 1 (3) ["John", empty, "Karan"]
When we check for items after deletion we see that there are still 3 items and the index 1 which we deleted is empty but
the index still exists if we call it we get `undefined`.
names[1] //Console output undefined
So in order to remove the item with index completely, we can use array method `splice()`.
Syntax
array.splice(index,delete_count);
It takes to arguments first the index to be deleted and the next number of items to be deleted. On calling this method will return deleted array items.
var names = ["John", "Rahul", "Karan"]; console.log("Before deleting item ",names); var index = 1; var del_count = 1; names.splice(1,1); console.log("After deleting item of index 1 ",names); //Console output Before deleting item (3) ["John", "Rahul", "Karan"] After deleting item of index 1 (2) ["John", "Karan"]