渐变显示地图数值echarts category配置项内容和展示

      function randomData() {
    return Math.round(Math.random()*2500);
}

option = {
    tooltip: {
        trigger: 'item',
        formatter: '{b}'
    },
    visualMap: {
        seriesIndex: 0,
        min: 0,
        max: 2500,
        left: 'left',
        top: 'bottom',
        text: ['高','低'],           // 文本，默认为数值文本
        calculable: true
    },
    grid: {
        height: 200,
        width: 8,
        right: 80,
        bottom: 10
    },
    xAxis: {
        type: 'category',
        data: [],
        splitNumber: 1,
        show: false
    },
    yAxis: {
        position: 'right',
        min: 0,
        max: 20,
        splitNumber: 20,
        inverse: true,
        axisLabel: {
            show: true
        },
        axisLine: {
            show: false  
        },
        splitLine: {
            show: false
        },
        axisTick: {
            show: false
        },
        data: []
    },
    series: [
        {
            zlevel: 1,
            name: '中国',
            type: 'map',
            mapType: 'china',
            selectedMode : 'multiple',
            roam: true,
            left: 0,
            right: '15%',
            label: {
                normal: {
                    show: true
                },
                emphasis: {
                    show: true
                }
            },
            data:[
                {name: '北京',value: randomData() },
                {name: '天津',value: randomData() },
                {name: '上海',value: randomData() },
                {name: '重庆',value: randomData() },
                {name: '河北',value: randomData() },
                {name: '河南',value: randomData() },
                {name: '云南',value: randomData() },
                {name: '辽宁',value: randomData() },
                {name: '黑龙江',value: randomData() },
                {name: '湖南',value: randomData() },
                {name: '安徽',value: randomData() },
                {name: '山东',value: randomData() },
                {name: '新疆',value: randomData() },
                {name: '江苏',value: randomData() },
                {name: '浙江',value: randomData() },
                {name: '江西',value: randomData() },
                {name: '湖北',value: randomData() },
                {name: '广西',value: randomData() },
                {name: '甘肃',value: randomData() },
                {name: '山西',value: randomData() },
                {name: '内蒙古',value: randomData() },
                {name: '陕西',value: randomData() },
                {name: '吉林',value: randomData() },
                {name: '福建',value: randomData() },
                {name: '贵州',value: randomData() },
                {name: '广东',value: randomData() },
                {name: '青海',value: randomData() },
                {name: '西藏',value: randomData() },
                {name: '四川',value: randomData() },
                {name: '宁夏',value: randomData() },
                {name: '海南',value: randomData() },
                {name: '台湾',value: randomData() },
                {name: '香港',value: randomData() },
                {name: '澳门',value: randomData() }
            ]
        },
        {
            zlevel: 2,
            name: '地图指示',
            type: 'bar',
            barWidth: 5,
            itemStyle: {
                normal: {
                    color: undefined,
                    shadowColor: 'rgba(0, 0, 0, 0.1)',
                    shadowBlur: 10
                }
            },
            data: [20]
        }
    ]
};


/**
 * 根据值获取线性渐变颜色
 * @param  {String} start 起始颜色
 * @param  {String} end   结束颜色
 * @param  {Number} max   最多分成多少分
 * @param  {Number} val   渐变取值
 * @return {String}       颜色
 */
function getGradientColor (start, end, max, val) {
    var rgb = /#((?:[0-9]|[a-fA-F]){2})((?:[0-9]|[a-fA-F]){2})((?:[0-9]|[a-fA-F]){2})/;
    var sM = start.match(rgb);
    var eM = end.match(rgb);
    var err = '';
    max = max || 1
    val = val || 0
    if (sM === null) {
        err = 'start';
    }
    if (eM === null) {
        err = 'end';
    }
    if (err.length > 0) {
        throw new Error('Invalid ' + err + ' color format, required hex color');	
    }
    var sR = parseInt(sM[1], 16),
        sG = parseInt(sM[2], 16),
        sB = parseInt(sM[3], 16);
    var eR = parseInt(eM[1], 16),
        eG = parseInt(eM[2], 16),
        eB = parseInt(eM[3], 16);
    var p = val / max;
    var gR = Math.round(sR + (eR - sR) * p).toString(16),
        gG = Math.round(sG + (eG - sG) * p).toString(16),
        gB = Math.round(sB + (eB - sB) * p).toString(16);
    return '#' + gR + gG + gB;
}

setTimeout(function() {
    var TOPN = 25
    
    var option = myChart.getOption()
    // 修改top
    option.grid[0].height = TOPN * 20
    option.yAxis[0].max = TOPN
    option.yAxis[0].splitNumber = TOPN
    option.series[1].data[0] = TOPN
    // 排序
    var data = option.series[0].data.sort(function(a, b) {
        return b.value - a.value
    })
    
    var maxValue = data[0].value,
        minValue = data.length > TOPN ? data[TOPN - 1].value : data[data.length - 1].value
    
    var s = option.visualMap[0].controller.inRange.color[0],
        e = option.visualMap[0].controller.inRange.color.slice(-1)[0]
    var sColor = getGradientColor(s, e, maxValue, minValue)
    var eColor = getGradientColor(s, e, maxValue, maxValue)
    
    option.series[1].itemStyle.normal.color = new echarts.graphic.LinearGradient(0, 0, 0, 1, [{
        offset: 1,
        color: sColor
    }, {
        offset: 0,
        color: eColor
    }])
    
    // yAxis
    var newYAxisArr = []
    echarts.util.each(data, function(item, i) {
        if (i >= TOPN) {
            return false
        }
        var c = getGradientColor(sColor, eColor, maxValue, item.value)
        newYAxisArr.push({
            value: item.name,
            textStyle: {
                color: c
            }
        })
    })
    option.yAxis[0].data = newYAxisArr
    option.yAxis[0].axisLabel.formatter = (function(data) {
        return function(value, i) {
            if (!value) return ''
            return value + ' ' + data[i].value
        }
    })(data)
    myChart.setOption(option)
}, 0);