bar-渐变色柱形图，tooltip小标签显示渐变颜色

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var legendData = ['A', 'B', 'C', 'D'];
var xData = ['1', '2', '3', '4', '5'];
var data1 = [10, 20, 30, 40, 50];
var data2 = [11, 21, 31, 41, 51];
var data3 = [12, 22, 32, 42, 52];
var data4 = [13, 23, 33, 43, 53];
var datas = [data1, data2, data3, data4];
var offsetcolor0 = ['rgb(255,182,193,1)', 'rgba(0,0,255,1)', 'rgb(0,205,102,1)', 'rgb(119,136,153,1)'];
var offsetcolor1 = ['rgb(255,182,193,.1)', 'rgba(0,0,255,.1)', 'rgb(0,205,102,.1)', 'rgb(119,136,153,.1)'];
// series值
var seriesData = [];
for (var i = 0; i < 4; i++) {
    var seriesData0 = {
        name: legendData[i],
        type: 'bar',
        data: datas[i],
        itemStyle: { //折线颜色不取渐变色，取color设置值
            normal: {
                color: new echarts.graphic.LinearGradient(
                    0, 0, 0, 1,
                    [{
                            offset: 0, //开始位置，从上向下
                            color: offsetcolor0[i]
                        },
                        {
                            offset: 1,
                            color: offsetcolor1[i]
                        }
                    ]
                )
            }
        },
    };
    // 填充到seriesData中
    seriesData.push(seriesData0);
}

option = {
    //定义线的颜色，series.type='line'取，series.type='bar'不取
    grid: {
        left: '20%',
        right: '20%',
        bottom: '20%',
    },
    tooltip: {
        trigger: 'axis',
        formatter: function(params) {
            var name = '时间：' + params[0].name + ":00<br/>"; //x轴名称
            var str = ''; //辅助变量，存储要展示的提示信息
            // 获取到各系列的渐变色
            var series_colors = [];
            for (var i = 0; i < params.length; i++) { // params.length为4，代表4个系列，每次悬浮时触发tooltip样式
                series_colors[i] = params[i].color.colorStops[0].color; //取到渐变色的值，也可以用offsetcolor0[i]代替
                // 重定义marker值
                params[i].marker = "<span style='display:inline-block;margin-right:5px;border-radius:10px;width:9px;height:9px;background-color:" + series_colors[i] + "'></span>";
                str = str + params[i].marker + params[i].seriesName + "：" + params[i].value + "<br/>";
            }
            // 返回结果值
            return name + str;
        },
    },
    legend: {
        data: legendData,
        selectedMode:false,//禁止选图例
    },
    calculable: true,
    xAxis: [{
        type: 'category',
        axisTick: {
            show: false
        },
        data: xData
    }],
    yAxis: [{
        type: 'value'
    }],
    series: [],
};
// 设置series值
option.series = seriesData;