2018-05-23

1.与运算符 &&
{unreadMessages.length > 0 &&

You have {unreadMessages.length} unread messages.

}
2.三目运算符

{isLoggedIn ? (

) : (

)}

3.箭头函数修改状态
handleToggleClick() {
this.setState(prevState => ({
showWarning: !prevState.showWarning
}));
}