react 給選中的li添加樣式

思路：使用事件委託，
關鍵：獲取到的index必須轉爲數字，由於它是字符串

handleClick = (e) => {
        const nodeName = e.target.nodeName.toUpperCase()
        let tag = e.target;
        if (nodeName === 'LI') {
            let index = parseInt(tag.getAttribute('index'))
            this.setState({
                currentIndex: index
            })
        }
    }

import React from 'react'import './nav.scss'class NavCom extends React.Component {    constructor(props) {        super(props)        this.state = {            currentIndex: 0        }    }    sestCurrentStyle = (index) => {        return this.state.currentIndex === index ? 'current' : ''    }    handleClick = (e) => {        const nodeName = e.target.nodeName.toUpperCase()        let tag = e.target;        if (nodeName === 'LI') {            let index = parseInt(tag.getAttribute('index'))            this.setState({                currentIndex: index            })        }    }    render() {        const navList = this.props.navList        return (            <div className='nav-wrap' onClick={(e)=>this.handleClick(e)}>                {                    navList && navList.map( (item, index) => {                        return (                            <li key={index} index={index} className={this.state.currentIndex === index ? 'current' : ''}>{item}</li>                        )                    })                }            </div>        )    }}export default NavCom