전개구문 Spread syntax : 배열

전개구문 Spread syntax : 배열

let arr1 =[1,2,3];
let arr2 =[4,5,6];
let result =[...arr1, ...arr2];

console.log(result);


전개구문 : 객체
let user ={name: 'Mike'}
let mike={...user, age:30}

console.log(mike) //{name:"Mike", age:30}

전개구문 : 복제
let arr=[1,2,3];
let arr2=[...arr];  //[1,2,3]

let user ={name : 'mike', age:30};
let user2={...user};

user2.name="tom";

console.log(user.name); //"mike"
console.log(user2.name);  //"tom"

//arr1을 [4,5,6,1,2,3]으로

let arr1=[1,2,3];
let arr2=[4,5,6];

arr2.reverse().forEach((num) =>{
arr1.unshift(num);
});

console.log(arr1);

===> 이것을 전개구문으로 표현하면 
let arr1=[1,2,3];
let arr2=[4,5,6];

arr1=[...arr2, ...arr1];

console.log(arr1);

**************************************************

전개구문으로 간단히 표현하는 연습을 해보자

 

let user={name:"mike"}; 
let info ={age:30};
let fe=["JS","React"];
let lang =["Korean","English"];

user=Object.assign({},user,info,{
  skills: [],
  
});
fe.forEach(item => {
  user.skills.push(item);
  
});
lang.forEach((item)=>{
  user.skills.push(item);
  
  
});
console.log(user);

===> 전개구문으로 고쳐보자!!

let user={name:"mike"}; 
let info ={age:30};
let fe=["JS","React"];
let lang =["Korean","English"];

user ={
  ...user,
  ...info,
 skills:[...fe, ...lang],
};

console.log(user);