Objects & Object oriented programming - LECTURE 3 | JavaScript Full Course | JavaScript for Beginner

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Objects & OOPS in
Javascript
Object properties Object Literals OOPS in Javascript Constructor Functions Inheritance

Objects in Javascript
The simple types of JavaScript are numbers, strings, booleans (true and false), null, and undefined. All other values are objects.
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•
•
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Property value can be static or dynamic which are functions(methods) Example {Car_Obj — name: Honda, year: 2018, age: currentyr-2018}
Objects in JavaScript are mutable keyed collections. In JavaScript,
arrays are objects, functions are objects, regular expressions are
objects, and, of course, objects are objects.
An object is a container of properties, where a property has a name and a value. A property name can be any string, including the empty
string.

Object Literals
• Object literals provide a convenient notation for creating new object values.
var flight = {
airline: "Oceanic",
number: 815,
departure: {
IATA: "SYD",
time: "2004-09-22 14:55",
city: "Sydney"
}, arrival: {
IATA: "LAX",
time: "2004-09-23 10:42",
city: "Los Angeles"
}, name_number: function(){return this.airline + this.number}
};

Object Literals
Updating property value can be done with a simple assignment
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A property's name can be any string, including the empty string. The
quotes around a property's name in an object literal are optional if the
the name would be a legal JavaScript name and not a reserved word.
dot operator can be used to retrieve properties “undefined” is produced when the property doesn’t exist


OOPs/OOJs in Javascript
•
JavaScript has a class-free object system[classes
introduced in ECMA 2015] in which objects inherit
properties directly from other objects.
Every object is linked to a prototype object from which it can inherit properties. All objects created from object literals are linked to Object prototype, an object
that comes standard with JavaScript.
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Functions in JavaScript are objects. Thus they can
have methods
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Constructor Function = Class

JavaScript uses special functions called constructor
functions to define and initialise objects and their features.
function Person(name) {
this.name=name;
this.greeting = function() {
alert('Hi! I\'m ' + this.name + '.');
};
}
Person1 = new Person(“john”);

Classes and Inheritance
“extends” keyword can help us create a sub-class of a parent class.

class Car {
constructor(brand) {
}
this.carname = brand;
present() {
}
return 'I have a ' + this.carname;
}
class Model extends Car {
constructor(brand, mod) {
super(brand);
this.model = mod;
}
show() {
}
return this.present() + ', it is a ' + this.model;
}

Problem
function Shape(name, sides, sideLength) { this.name = name;
this.sides = sides;
this.sideLength = sideLength;
}
//
Add a new method to the Shape class's prototype, calcPerimeter(), which calculates its perimeter (the length of the shape's outer edge) and logs the result to the console.
Create a new instance of the Shape class called square. Give it the name of a square and a sideLength of 5.
Call your calcPerimeter()

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