echarts3里formatter不生效echarts category配置项内容和展示

在第一个series里，设置了label为emphasis时显示文本的格式不生效，但是如果改emphasis为normal时，formatter才生效。但是echarts3里的文档写着normal和emphasis的用法是一样的啊

      option = {
    title: {
        text: '折线图堆叠',
        top: 0
    },
    tooltip: {
        trigger: 'axis',
        formatter: function (params) {
            var content = params[0].name;
            if (params[0].name == 0) {
                content = '';
            }
            else {
                content += '<br>'
            }
            content += '<span style="display:inline-block;margin-right:5px;border-radius:10px;width:9px;height:9px;background-color:' + params[0].color + '"></span>';
            content += params[0].seriesName + ' : ';
            content += params[0].value.toFixed(2) + '<br>';
            content += '<span style="display:inline-block;margin-right:5px;border-radius:10px;width:9px;height:9px;background-color:' + params[1].color + '"></span>';
            content += params[1].seriesName + ' : ';
            content += (params[1].value * 100).toFixed(2) + '%'
            return content;
        }
    },
    legend: {
        data:['avgranking','关键词覆盖度']
    },
    grid: {
        left: '3%',
        right: '4%',
        bottom: '3%',
        containLabel: true
    },
    xAxis: {
        name: '小时',
        nameGap: 20,
        nameTextStyle: {
            color: '#696969'
        },
        type: 'category',
        boundaryGap: true,
        axisTick: {
            inside: true
        },
        axisLine: {
            lineStyle: {
                color: '#b7b9bd'
            }
        },
        axisLabel: {
            textStyle: {
                color: '#696969'
            }
        },
        data: ['0','1','2','3','4','5','6','7','8','9','10','11']
    },
    yAxis: [
        {
            type: 'value',
            axisLine: {
                show: false
            },
            axisTick: {
                show: false
            },
            axisLabel: {
                textStyle: {
                    color: '#696969'
                }
            },
            max: 1.8,
            splitLine: {
                show: false
            }
        },
        {
            type: 'value',
            axisLine: {
                show: false
            },
            axisTick: {
                show: false
            },
            splitLine: {
                show: false
            },
            max: 0.8,
            axisLabel: {
                formatter: function (value, index) {
                    if (index === 0) {
                        return 0;
                    }
                    return (value * 100).toFixed(2) + '%';
                },
                textStyle: {
                    color: '#696969'
                }
            }
        }
    ],
    series: [
        {
            name:'avgranking',
            type:'line',
            symbol: 'circle',
            symbolSize: 7,
            label: {
                emphasis: {
                    show: true,
                    formatter: (item) => {
                        return item.value.toFixed(2);
                    }
                }
            },
            data:[1.6972807491446065, 1.687272396212673, 1.689159494598059, 1.6954452118723167, 1.6801678703884442, 1.6630155910795343, 1.6596720671481553, 1.649119392818916, 1.6637633996937213, 1.6784004505773022, 1.6723142803947124, 1.6881126358937801]
        },
        {
            name:'关键词覆盖度',
            type:'line',
            yAxisIndex: 1,
            symbol: 'circle',
            symbolSize: 7,
            data:[0.7997987927565392,
                  0.7686116700201208, 
                  0.772635814889336, 
                  0.7585513078470825, 
                  0.7334004024144869, 
                  0.7223340040241448, 
                  0.7223340040241448, 
                  0.7354124748490946, 
                  0.7414486921529175, 
                  0.7605633802816901, 
                  0.7716297786720322, 
                  0.7907444668008048
                 ]
        }
    ]
};