react.js:3640 Warning: Each child in an array or iterator should have a unique "key" prop. Check the render method of UserList. See https://fb.me/react-warning-keys for more information.
in h3 (created by UserList)
in UserList
加上 key 啥箭， 如下：
render: function () {
var createItem = function (u) {
return (<h3 key={'li_' + u.id}> {u.username + ':' + JSON.stringify(u.roles)}</h3>);
}
return (
<ul>
{this.state.users.map(createItem)}
</ul>
);
}
