Object-oriented programming In Javascript

objects Literal :- You Just Literaly Open And Close a curly braces and write properties and methods

Factory Function: you Create a function and inside the function retun the object literal , and to call it declar a variable and call the function

constructor Function: You create a function and use this to assign properties and methods and use new keyword along with function name to create an instance of the constructor; (Constructor Functions Start With An Upper case letter)

Functions Are Objects :-

note ["every object in js has an constructor property"]

note ["When We Create a function using This Syntax [ function circle(){}"] internaly Function constructor runs and create the function ]

values :- copies Value

reference :- copies reference

Adding and deleting Properties :- you can add a property by just writeing the Instance name Either . Or [] And Then Add Like Object literal

to delete write delete in front of the objcet

Enumearting properties: You can Enumearte over properties by a for loop like

function Circle(radies){

this.radies = radies;

this.draw = function() {

console.log('draw');

}

const circle = new Circle(10);

for (let key in circle){

console.log(key, circle[key]);

}

Objcet.keys(circle); / It Returens all the keys in the circle object as an array;

check the existance of a property or method in an object use

example

if ('radies' in circle){

// do something

}

Abstraction

in javascript we use let to declar private variable if we have a function and inside it we have properties and methods that we wanted to make private we must make them local varibale or local function using let

clousers in javascript

in clousers we preserve the local variable and function if they are user in any child function of that function

Getters And Setters

the Problem with Setting private variable and function is that You cant access Them in other places

but if you want yo show them then either use this.getFunctionName = () =>{

return the variable;

};

or you can use Objcet.defineProperties() to set up getters and setters

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In Javascript we do not have classes we have objects thats why in js we use prototypical inheritance

prototype is just an object it self but prototype is just parent in js a object inherits from its parent

every object In js has a perent its '__proto__' or prototype just __proto__ dont have __proto__

prototypical inheritance :- if we use a method in our javascript objcet but dont define it javascript engine check to its parent all the waty to '__proto__' ;

Multilevel inheritance :-

in js when we declar an empty array what happends is its get inherited from arraybase or prototype and create an array but the prototype is it self an object and get inherited from __proto__ or prototype its an example of multilevel inheritance

Note** all object created by the object constructor would have the same prototype

Property Descriptors

constructor Properties

you can get the prototype by either myobj.__proto__ or Objcet.getPrototypeOf(myobj)

it retun the all the prototypes in this objcet

in javascript function are also objcets

prototypes Properties and method vs instance Properties and method

take method from instance members and put it into objcet base

function Circle(){

this.draw()= () =>{

something

}

};

to add on objcet base

Circle.prototype.draw=() => {

something

} ;

javascript specificity 101

if you have a method in instance members and properties members javascript is first gona look at the instance members and then go to prototype members

opps In Javascript (Brad Traversy)

prototypical inheritance

.call() => method call allows us to call other function from other places in the current context

inherits the person prototype method

Customer.prototype = Object.create(Person.prototype)

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Using Object.create

or we can use js classes (es6)

es6 static method

put static before a function and call using class name

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modules in js