arr.map(callback, [thisArg])
var numbers = [1,2,3,4,5];
var processed = numbers.map(function(num){
return num * num;
});
console.log(processed);
//RESULT
[1,4,9,16,25]
import React, { useState } from 'react';
const IterationSample = () => {
const [names, setNames] = useState([
{ id:1 , text: '눈사람' },
{ id:2 , text: '얼음' },
{ id:3 , text: '눈' },
{ id:4 , text: '바람' },
]);
const [inputIndex, setInputIndex] = useState('');
const [nextId, setNextId] = useState(5); //새로운 항목 추가시 사용하는 id
const onChange = e => setInputText(e.target.value);
const onClick = () => {
const nextNames = names.concat({
id: nextId, //nextId값을 id로 설정
text : inputText
});
setNextId(nextId + 1);
setNames(nextNames);
setInputText('');
};
const namesList = names.map(name => <li key={name.id}> {name.text} </li>);
return (
<>
<input value = {inputText} onChange={onChange} />
<button onClick={onClick}>추가</button>
<ul>{namesList}</ul>
</>
);
};
export default IterationSample;