JS [Object]

// Objects

// one of the JavaScript's data types.

// a collection of related data and/or functionality.

// Nearly all objects in JavaScript are instances of Object

// Object = {key : value}

// 1. Literals and properties

const obj1 = {}; // 'object literal' syntax

const obj2 = new Object(); // 'object constructor' syntax

function print(person){

    console.log(person.name);

    console.log(person.age);

}

const ellie ={name:'ellie', age:4};

print(ellie);

// JS는 runtime에서 동작하므로 dynamic 코딩이 가능함

ellie.hasjob =true;

console.log(ellie.hasjob);

delete ellie.hasjob;

console.log(ellie.hasjob);

// 2. Computed properties

//key should be always string

console.log(ellie.name);

console.log(ellie['name']);

ellie['hasjob']=true;

console.log(ellie.hasjob);

// 모르는 값을 받아 접근 할때는 []를 사용

function printValue(obj,key){

    console.log(obj[key]);

}

printValue(ellie,'name');

printValue(ellie,'age');

//3. Propery value shorthand

const person1 = {name:'bob',age:2};

const person2 = {name:'bobi',age:3};

const person3 = {name:'apple',age:4};

const person4 = new Person('ellie',30);

// 4. Constructor function

function Person(name,age){

    // this={}

    this.name=name;

    this.age=age;

    // return this

}

// 5. in operator : property existence check (key in obj)

console.log('name' in ellie);

console.log('age' in ellie);

console.log('random' in ellie);

console.log(ellie.random);

// 6. for..in vs for..of

// for (key in obj)

for (let key in ellie){

    console.log(key);

}

// for (value of iterable)

const array =[1,2,4,5];

for (value of array){

    console.log(value)

}

// 7. Fun cloning

// Object.assing(dest, [obj1, obj2, obj3 ...])

const user = {name:'ellie', age:20};

const user2=user;

user2.name='coder';

console.log(user);

//old way

const user3 ={};

for (key in user){

    user3[key]=user[key];

}

console.log(user3);

//recently used way

const user4 = Object.assign({},user);

// another example

const fruit1= {color:'red'};

const fruit2= {color:'blue', size:'big'};

const mixed = Object.assign({},fruit1,fruit2);

console.log(mixed.color);

console.log(mixed.size);