map 함수를 이용해서 여러개 출력
function NumberList(props){
const numbers = props.numbers;
const listItems = numbers.map((number)=>
<li>{number}</li>);
return (
<ul>{listItems}</ul>);}
const numbers =[1,2,3,4,5]
ReactDOM.render(
<NumberList numbers={numbers}/>,
document.getElementById('root'));
const listItems = numbers.map((**number**)=>
<li **key={number.toString()**}>{number}</li>);
id가 존재한다면?
cosnt todoItems = todos.map((todo)=>
<li **key={todo.id}**> {todo.text}</li>);
id가 존재 안한다면? index 사용 (권유 안함)
cosnt todoItems = todos.map((todo,index)=>
<li **key={index}**> {todo.text}</li>);
class AttendanceBook extends React.Component{
constructor(props){
super(props);
this.state = {
students:[
{name:'Mike'},{name:'hommy'},{name:'jake'},{name:'susan'},
{name:'yoshi'},{name:'mario'},{name:'luige'},{name:'koopa'},]
}
}
render(){
var students = this.state.students
return (
<ul>
{students.map((student,index)=>
<li **key={index**} >{student.name}</li>)}
</ul>
)
}
}
export default AttendanceBook