js中类成员可以用什么样的方式定义,好多地方都没有说明,今天调试一段代码正好又遇到了这个问题,代码如下:

import React from 'react'
import ReactDOM from 'react-dom'
import iScroll from 'iscroll'

import './example.css'
import ReactIScroll from 'react-iscroll'

const iScrollOptions = {
    mouseWheel: true,
    scrollbars: true,
    scrollX: true
};

class JsPage extends React.Component {

    constructor(props) {
        super(props)

        const list = [];
        const len = 30;

        for(let i = 0; i < len; i++) {
            list.push(i+1)
        }

        this.state = {
            y: 0,
            isScrolling: false,
            list: list,
            lastId: len
        }
    }

    onScrollStart = () => {
        this.setState({isScrolling: true})
    }; 

    onScrollEnd = (iScrollInstance) => {
        this.setState({isScrolling: false, y: iScrollInstance.y})
    };

    addRow = (ev) => {
        ev.preventDefault()

        const list  = this.state.list,
              newId = this.state.lastId + 1;

        list.push(newId)

        this.setState({list: list, lastId: newId})
    };

    removeRow = (ev) => {
        ev.preventDefault()

        const list = this.state.list;

        list.shift()

        this.setState({list: list})
    };

    onScrollRefresh = (iScrollInstance) => {
        const hasVerticalScroll = iScrollInstance.hasVerticalScroll

        if(this.state.canVerticallyScroll !== hasVerticalScroll) {
            this.setState({canVerticallyScroll: hasVerticalScroll})
        }
    };

    render() {
        const listOfLi = [],
              len = this.state.list.length;
        let i = 0;

        for(i; i < len; i++) {
            listOfLi.push(
Pretty row {this.state.list[i]}I'm beyond
)
        }
        return (
            

                

                    Remove first row
                    React iScroll component example
                
                

                    
                        

                            

                                {listOfLi}
                            
                        

                    
                

                

                    Add one row
                    status: {this.state.isScrolling ? 'Scrolling' : 'Standby' } |
                    can vertically scroll: {this.state.canVerticallyScroll ? 'Yes' : 'No'}
                
            

        )
    }
}

export default JsPage;

报错信息如下:

ERROR in ./master/jsx/components/jspage.jsx
Module build failed: SyntaxError: C:/codes/ihotel/src/jspage.jsx: Unexpected token (34:18)
  32 |     }
  33 |
> 34 |     onScrollStart = () => {
     |                   ^
  35 |         this.setState({isScrolling: true})
  36 |     };
  37 |

类成员不能用箭头函数赋值吗?