오브젝트

ex)

//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 name = 'han';
const age = 4;
print(name, age);
function print(name, age){
    console.log(name);
    console.log(age);
}

const jin = {name: 'jin', age:27};
function print(person){
    console.log(person.name,person.age);
}
print(jin);

//가능한 이렇게 코딩하지 말것
jin.hasJob = true;
console.log(jin.hasJob);

delete jin.hasJob;
console.log(jin.hasJob);

 

예제 실행 화면

 

ex)

//2. Computed properties
//key should be always string
const jin = {name: 'jin', age:27};
console.log(jin.name);
console.log(jin['name']);
jin['hasJob'] = true;
console.log(jin.hasJob);

function printValue(obj, key){
    console.log(obj.key);
    console.log(obj[key]);
}
printValue(jin,'name');
printValue(jin,'age');

 

예제 실행 화면

 

ex)

//3.Property value shorthand
const person1 = {name: 'bob', age: 2};
const person2 = {name: 'steve', age: 3};
const person3 = {name: 'dave', age: 4};
const person4 = new Person('jin', 30);
console.log(person4);

//4. Constructor Function
function Person(name, age){
    //this = {};
    this.name = name;
    this.age = age;
    //return this;
}

 

예제 실행 화면

 

ex)

//5. in operator: property existence check (key in obj)
const jin = {name: 'jin', age:27};
console.log('name' in jin);
console.log('random' in jin);
console.log(jin.random);

 

예제 실행 화면

 

ex)

//6. for..in vs for..of
//for(key in obj)
const jin = {name: 'jin', age:27};
for(key in jin){
    console.log(key);
}

//for(value of iterable)
const array = [1,2,4,5];
for(let i = 0; i < array.length; i++){
    console.log(array[i]);
}
for(value of array){
    console.log(value);
}

 

예제 실행 화면

 

ex)

//7. Fun cloning
//Object.assign(des, [obj1, obj2, obj3...])
const user = {name: 'jin', age: '20'};
const user2 = user;
user2.name = 'han';
console.log(user);

//old way
const user3 = {};
for(key in user){
    user3[key] = user[key];
}
console.log(user3);

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

//another example
const fruit1 = {color: 'red'};
const fruit2 = {color: 'blue', size: 'big'};
const mixed = Object.assign({},fruit1, fruit2); // 같은 key는 뒤로 가면서 계속 덮어쓰기함
console.log(mixed.color);
console.log(mixed.size);

 

예제 실행 화면