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Objects are the collection of properties which contain values as key:value pairs.
A property is also like a variable which stores data, but in property we stores
data in key:value pair i.e, age:21
We access property of an objects by object_name.property_name
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var person = {
first_name : "Marty",
last_name : "Mcfly",
born : 1968,
died : 1933,
lovers: ["Jennifer Parker","Baines McFly"]
};
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/*
An object is made of key value pairs. Keys can be strings
(which don't require quotes), array with a string, or symbols. Values can be arrays,
objects, numbers etc
*/
let testSymbol = Symbol('item number 3')
const obj = {
item1: 1,
"item number 2": 2,
testSymbol: 3,
['a']: 4
}
// Another way of creating an object:
const obj = new Object();
obj.name = 'John'
// To access values, you can use dot notation or bracket notation.
// Both do the same thing, bracket notion is useful for multispace keys,
// keys with dashes, or accessing values using variables
> obj.item1
> obj['item number 2']
> let b = 'item1'
obj[b]
// The following would NOT work and would return undefined:
obj.b
// Checking exsistence of keys in object:
obj.toString ----- checks values of object and whatever object inherits from
> returns true
obj.hasOwnProperty('toString') ----- checks values of object only. Do this instead of checking like: (obj.name !== undefined)
> returns false
// Short hand key assignment:
const name = 'John'
const obj2 = {
// this is short hand that automatically sets the key to be 'name',
// and it's value to be 'John'
name,
}
// Constructor objects:
function Obj(name, age){
this.name = name
this.age = age
}
const person = new Obj('john', 1)
// adding functions, couple ways:
const obj = {
name: 'Mike',
number: 4421,
sayHi: () => console.log('hi'),
sayBye() {
console.log('say bye')
},
// getter function to get values from object. Has different usecases, but the same as doing obj.number
get getNumber(){
return this.number
}
// setter function to set values in object. Has different usecases, but the same as doing obj.number = 152
set setNumber(num){
this.number = num
}
}
obj.sayHi()
obj.sayBye()
obj.getNumber //Note how it's being accessed like a standard property, and not a function
obj.setNumber //Note how it's being accessed like a standard property, and not a function
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1) Object Literal
const obj = {
name: "Ram",
age: "20"
}
2) Constructor Function or ES6- Class
const a = new Person("Ram", "25") //given Person is an existing function or class
3) Object.create method
const ram = Object.create(Person); //given person is an existing object
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The Object is the real-time entity having some state and behavior.
In Java, Object is an instance of the class having the instance variables
as the state of the object and the methods as the behavior of the object.
The object of a class can be created by using thenewkeyword
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var myObject = {}; // Empty object
// Object with properties
var person = {
name: "John Doe",
age: 30,
occupation: "Developer"
};
console.log(person.name); // Output: "John Doe"
console.log(person.age); // Output: 30
console.log(person.occupation); // Output: "Developer"
object in js
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const person = {
firstName: 'John',
lastName: 'Doe',
age: 30
};
console.log(person); // logs {firstName: "John", lastName: "Doe", age: 30}
The object data type is used to represent a collection of key-value pairs. An object can be created using the curly braces {} syntax or the new Object() syntax. For example:
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const obj = {
name: "Mon contenu",
id: 1234,
message: "Voici mon contenu",
author: {
name: "John"
},
comments: [
{
id: 45,
message: "Commentaire 1"
},
{
id: 46,
message: "Commentaire 2"
}
]
};
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// Using object literal notation
const person = {
name: 'John Doe',
age: 30,
occupation: 'Developer',
};
// Accessing object properties
console.log(person.name); // Output: John Doe
console.log(person.age); // Output: 30
console.log(person.occupation); // Output: Developer
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// JavaScript objects are a fundamental data structure used to represent various entities.
// They have properties that can be used to store key-value pairs of data.
// Create an object using object literal notation
const person = {
name: "John",
age: 25,
city: "New York"
};
// Accessing object properties
console.log(person.name); // Output: "John"
console.log(person.age); // Output: 25
// Adding a new property to the object
person.gender = "Male";
// Updating an existing property
person.age = 26;
// Deleting a property
delete person.city;
// Looping through object properties
for (let key in person) {
console.log(key + ": " + person[key]);
}
// Output:
// name: John
// age: 26
// gender: Male