TypeError: react__WEBPACK_IMPORTED_MODULE_0___default.a.createClass is not a function

1、错误描述

2、错误原因

import React, {Component} from 'react';
import {render} from 'react-dom';
import Button from 'react-bootstrap/Button';

var TickTock = React.createClass({
mixins: [SetIntervalMixin], 
getInitialState: function() {
return {seconds: 0};
    },
componentDidMount: function() {
this.setInterval(this.tick, 2000); 
    },
tick: function() {
this.setState({seconds: this.state.seconds + 1});
    },
render: function() {
return (
<label>
                {this.state.seconds} seconds.
</label>
        );
    }
});

     由错误提示可知，是React.createClass不是一个函数（方法）

3、解决办法