Objects

Estimated reading time: 8 minutes
  • objects is a collections of data . objects represent by { ... } or array objects [{},{}] . objects is name value pair base.

create objects

  • constructor
let users = new Object()
  • literal object with square bracket {..}
let users = {
  ......
}

let users = {
  name: 'kamal',
  age: 21,
  phone: 8123
}
console.log(users.name);
// kamal

let users = {
  name: 'kamal',
  age: 21,
  phone: {
    home: 88012,
    office: 121
  }
}
console.log(users.phone.office);
// 121

let users = [
  {name: 'kamal', age: 21},
  {name: 'jamal', age: 23},
  {name: 'maruf', age: 6}
]
users.forEach((user) => {
  console.log(user.name);
})
// kamal , jamal , maruf
  • es6 loop
let users = [
  {name: 'kamal', age: 21 ,post: 'marketer'},
  {name: 'jamal', age: 23, post: 'civil'},
  {name: 'maruf', age: 6, post: 'ceo'}
]
 for (let {name,post} of users) {
  console.log(`${name} is posted as ${post}`);
}
// kamal isposted as marketer
// jamal is posted as civil
// maruf is posted as ceo

multiword property

set

let users = {
  name: 'kamal',
  age: 21,
  phone: 017
}
users['salary rate'] = 2000;
console.log(users);
// {name: "kamal", age: 21, phone: 15, salary rate: 2000}

get

let users = {
  name: 'kamal',
  age: 21,
  phone: 017
}
users['salary rate'] = 2000;
console.log(users['salary rate']);
// 2000

delete

let users = {
  name: 'kamal',
  age: 21,
  phone: 017
}
users['salary rate'] = 2000;
delete users['salary rate'];
console.log(users['salary rate']);
// undefined
// deleted

method lists

methods methods methods
Object.assign() Object.create() Object.defineProperty()
Object.defineProperties() Object.entries() Object.freeze()
Object.getOwnPropertyDescriptor() Object.getOwnPropertyDescriptors() .
Object.getOwnPropertyNames() Object.getOwnPropertySymbols() Object.values()
Object.getPrototypeOf() Object.is() Object.isExtensible()
Object.isFrozen() Object.isSealed() Object.keys()
Object.preventExtensions() Object.seal() Object.setPrototypeOf()

assign

  • copy / clone
  • target ... source
let users = {
  name: 'kamal',
  age: 21,
  phone: '0172'
}
let admin = Object.assign({},users);
console.log(admin);
// {name: "kamal", age: 21, phone: "0172"}

entries

  • return key and value array .
let users = {
  name: 'kamal',
  age: 21,
  phone: '0172'
}
let result = Object.entries(users);
console.log(result);
result.forEach (([key,value]) => {
  console.log(`${key} is ${value}`);
})

// 0: ["name", "kamal"]
//1:["age", 21]
// 2: ["phone", "0172"]


// name is kamal
// age is 21
// phone is 0172

freeze

  • freeze method make objects constant , can’t add or delete objects properties.

~ output same

let users = {
  name: 'kamal',
  age: 21,
  phone: '0172'
}
let result = Object.freeze(users);
users['position'] = 'coder';
delete users['name'];
console.log(users);
// {name: "kamal", age: 21, phone: "0172"}

~ strict mode

'use strict';
let users = {
  name: 'kamal',
  age: 21,
  phone: '0172'
}
let result = Object.freeze(users);
users['position'] = 'coder';
delete users['name'];
console.log(users);
// Cannot add property position, object is not extensible

getOwnPropertyDescriptor

let users = {
  name: 'kamal',
  age: 21,
  phone: `567`
}

let result = Object.getOwnPropertyDescriptor(users,name);
console.log(result.value)
// kamal

getOwnPropertyDescriptors

let users = {
  name: 'kamal',
  age: 21,
  phone: `567`
}

let result = Object.getOwnPropertyDescriptors(users);
console.log(result.name.value);
console.log(result.age.value);
// kamal
// 21

getOwnPropertyNames

let users = {
  name: 'kamal',
  age: 21,
  phone: `567`
}
let result = Object.getOwnPropertyNames(users);
console.log(result);
// ["name", "age", "phone"]

getPrototypeOf

let users = {
  name: 'kamal',
  age: 21,
  phone: `567`
}
let mk = Object.create(users);
console.log(Object.getPrototypeOf(mk) === users);
// true

is

let result = Object.is('kamal', 'kamal')
console.log(result)
//  true

keys

let users = {
  name: 'kamal',
  age: 21,
  phone: `567`
}
let result = Object.keys(users);
console.log(result);
// ["name", "age", "phone"]

values

let users = {
  name: 'kamal',
  age: 21,
  phone: `567`
}
let result = Object.values(users);
console.log(result);
// ["kamal", 21, "567"]

resource

js