String , Array

 

String 에 새로운 메서드들!

 

startsWith 와 endsWith, includes 가 있다

 

let str="ryu is last name";

let matchstr="ryu";      

console.log(str.startsWith(matchstr));  // ryu로 시작하여 true

let matchstr2="name";

console.log(str.endsWith(matchstr2)); // name으로 끝나는게 맞으므로 true

let matchstr3="first name";

console.log(str.includes(matchstr3)); // first name 포함하지 않으므로 false

 

---

 

배열 순회하기 

 

for of 

 

for in의 문제점 보완하였다.

 

let arr=[1,2,3,"hi","hello"];

for(let v of arr){
console.log(v);    // 1,2,3,"hi","hello"
}

 

배열 뿐이 아니라 문자열도 가능하다

 

let str="my nickname is ryu";

for(let v of str){
console.log(v);
}

// "m","y"," ","n","i"...

 

---

spread operator :펼침 연산자

 

let sports=["soccer","basketball","golf"];

let newdata=[...sports];

console.log(sports); // "soccer","basketball","golf"

console.log(newdata);// "soccer","basketball","golf"

 

병합,함수에서도

 

let sports=["soccer","backetball","golf"];

let newsports=[...sports,"baseball"];

console.log(sports); // 그대로

console.log(newsports); // "soccer","backetball","golf","baseball"

 

function sum(a,b){
return a+b;
}

let arr=[10,20];

console.log(sum(...arr)); // 30

 

from 메서드

 

function gaga(){

let newdata=[];

for(let i=0;arguments.length;i++){
newdata.push(arguments[i]+"hi");
}
console.log(newdata);
}
gaga(1,2,3);  // "1hi","2hi","3hi"