There is  no Arrays in JavaScript!

There is no Arrays in JavaScript!

If you are using JavaScript often or frequently in your development, so you likely used arrays many times and you may consider it as one of the javascript data types, don’t be shocked but actually this not true!

1- What is the data types in JavaScript?

JavaScript has two types of data types, Primitive datatypes and Complex data types

Primitive data types is String, Number, Boolean, Undefined and Function

Any other data types is belong to Object data type!

2- What is the origin of Arrays!?

if we have an array and trying to now it’s type you might think of using the keyword typeof

var users=['John','Joe','Sandy'];
typeof users //output: Object

So what is the origin of arrays. Arrays is an inherited prototype from the type ‘Object’

3- What is the inheritance in JavaScript?

Although JavaScript doesn’t support standard OOP, but we code simulate a base class using the function declaration like the following

function Car(model,color,year){

“this” keyword here refers to any instance will be created from the class Car using “new” keyword

var car = new Car('BMW','blcak',1990);

Now let’s add some methods to this class using ‘prototype’ property which define all methods can be used with our Car data type i.e any new instances created from Car class. this the same as you use ‘length’ prototype property which retrieving the number of elements for any array


Now let’s create a child class named ChildCar which inherit from Car

function ChildCar(model,color,year){
ChildCar.prototype=Car.prototype; //inherit Car prototype
var newChild = new ChildCar("Ferarri","blue",2017);

Now we can use the method “incrementYear” on the instance newChild but we can’t use the method “changeModel” on the instance “car”

 console.log(newChild.year) //2018

but how should we now the type of the newChild? we have to use instanceof

 typeof car // Object
 typeof newChild // Object
 car instanceof Car //true
 newChild instanceof Car //true
 newChild instanceof ChildCar //true
 car instanceof ChildCar //false

So Array is …

Arrays is an inherited prototype of object via new class called Array so we can check of this like

 var users=['John','Joe','Sandy'];
 typeof users //output: Object
 users instanceof Array //true