1、React在ES6的实现中去掉了getInitialState这个hook函数，规定state在constructor中实现，如下：
Class App extends React.Component {
constructor(props) {
super(props);
this.state = {};
}
}
1、React在ES6的实现中去掉了getInitialState这个hook函数，规定state在constructor中实现，如下：
Class App extends React.Component {
constructor(props) {
super(props);
this.state = {};
}
}