如何添加使用echats地图悬浮显示内容

/初始化绘制全国地图配置
var option = {
    backgroundColor: '#000',
    title: {
        text: 'Echarts3 中国地图农村金融',
        subtext: '三级科技下乡',
        link: 'http://www.cnblogs.com/sxz2008/',
        left: 'center',
        textStyle: {
            color: '#fff',
            fontSize: 16,
            fontWeight: 'normal',
            fontFamily: "Microsoft YaHei"
        },
        subtextStyle: {
            color: '#ccc',
            fontSize: 13,
            fontWeight: 'normal',
            fontFamily: "Microsoft YaHei"
        }
    },
    tooltip: {        //显示悬浮窗口
        trigger: 'item',<br>         //使用这个函数返回悬浮内容
        <strong>formatter:function(params){</strong>
            //定义一个res变量来保存最终返回的字符结果,并且先把地区名称放到里面
            // var res='随机数字'+'<br />';
            var res=params.name+':'+'随机数字'+'<br />';
            var myseries=provinces;//省市区
            for(var i=0;i<myseries.length;i++){
                    if(myseries[i].name==params.name){
                        res+=myseries[i].name+':'+myseries[i].value+'<br />';
                    }
            }<br>　　　　　　　　//市区
            for(var j=0;j<city.length;j++){
                    if(city[j].name==params.name){
                      
                        res+=city[j].name+':'+city[j].value+'<br />';
                    }
                
            }<br>　　　　　　　　//县区
            for(var k=0;k<area.length;k++){
                    if(area[k].name==params.name){
                        res+=area[k].name+':'+area[k].value+'<br />';
                    }
            }
            return res;                
        },
         
             
    },
    toolbox: {
        show: true,
        orient: 'vertical',
        left: 'right',
        top: 'center',
        feature: {
            dataView: {
                readOnly: false
            },
            restore: {},
            saveAsImage: {}
        },
        iconStyle: {
            normal: {
                color: '#fff'
            }
        }
    },
    visualMap: {
        type: 'continuous', // 连续型
        min: 0, // 值域最小值，必须参数
        max: 1200, // 值域最大值，必须参数
        calculable: true, // 是否启用值域漫游
        inRange: {
            color: ['#50a3ba', '#eac736', '#d94e5d']
            // 指定数值从低到高时的颜色变化
        },
        textStyle: {
            color: '#fff' // 值域控件的文本颜色
        }
    },
     
    animationDuration: 1000,
    animationEasing: 'cubicOut',
    animationDurationUpdate: 1000
 
};