echart tooltip循环显示，legend随tooltip滚动循环显示

option = {
    title: {
        text: '饼图程序调用高亮示例',
        left: 'center'
    },
    tooltip: {
        trigger: 'item',
        formatter: '{a} <br/>{b} : {c} ({d}%)'
    },
    legend: {
        id: "stock-model",
        type: 'scroll',
        orient: 'vertical',
        top: 500,
        left: 'left',
        data: ['直接访问', '邮件营销', '联盟广告', '视频广告', '搜索引擎',
        '直接访问2', '邮件营销2', '联盟广告2', '视频广告2', '搜索引擎2'
        ]
    },
    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'},
                {value: 335, name: '直接访问2'},
                {value: 310, name: '邮件营销2'},
                {value: 234, name: '联盟广告2'},
                {value: 135, name: '视频广告2'},
                {value: 1548, name: '搜索引擎2'}
            ],
            emphasis: {
                itemStyle: {
                    shadowBlur: 10,
                    shadowOffsetX: 0,
                    shadowColor: 'rgba(0, 0, 0, 0.5)'
                }
            }
        }
    ]
};

app.currentIndex = -1;

setInterval(function () {
    var dataLen = option.series[0].data.length;
    // 取消之前高亮的图形
    myChart.dispatchAction({
        type: 'downplay',
        seriesIndex: 0,
        dataIndex: app.currentIndex
    });
    app.currentIndex = (app.currentIndex + 1) % dataLen;
    // 高亮当前图形
    myChart.dispatchAction({
        type: 'highlight',
        seriesIndex: 0,
        dataIndex: app.currentIndex
    });
    // 显示 tooltip
    myChart.dispatchAction({
        type: 'showTip',
        seriesIndex: 0,
        dataIndex: app.currentIndex
    });
    
    myChart.dispatchAction({
        type: 'legendScroll',
        scrollDataIndex: app.currentIndex,
        legendId: 'stock-model',
    });
}, 1000);