关于echarts中的饼状图的label文字显示过长的问题

Question

如图所示怎么设置当文字超过4个以后就进行换行呢

option = {
    title : {
        text: '某站点用户访问来源',
        subtext: '纯属虚构',
        x:'center'
    },
    tooltip : {
        trigger: 'item',
        formatter: "{a} <br/>{b} : {c} ({d}%)"
    },
    legend: {
        orient: 'vertical',
        left: 'left',
        data: ['直接访问','邮件营销','联盟广告','视频广告','搜索引擎']
    },
    series : [
        {
            name: '访问来源',
            type: 'pie',
            radius : '55%',
            center: ['50%', '60%'],
            data:[
                {value:335, name:'直接访问'},
                {value:310, name:'邮件营销'},
                {value:234, name:'联盟广告'},
                {value:135, name:'视频广告'},
                {value:1548, name:'搜索引擎'}
            ],
            itemStyle: {
                emphasis: {
                    shadowBlur: 10,
                    shadowOffsetX: 0,
                    shadowColor: 'rgba(0, 0, 0, 0.5)'
                }
            }
        }
    ]
};

Answer 1

option = {
    //...option
    series : [{
        //...series
        label:{
            normal:{
                formatter(v) {
                    let text = v.name
                    return text.length < 4 
                        ? text 
                        : `${text.slice(0,4)}\n${text.slice(4)}`
                }
            }  
        }
    }]
};

Answer 2