设置Echarts鼠标悬浮样式

 tooltip: {
                        show: true,
                        trigger: ‘axis‘,
                        //show: true,   //default true
                        showDelay: 0,//显示延时，添加显示延时可以避免频繁切换
                        hideDelay: 50,//隐藏延时
                        transitionDuration: 0,//动画变换时长
                        backgroundColor: ‘rgba(0,0,0,0.7)‘,//背景颜色（此时为默认色）
                        borderRadius: 8,//边框圆角
                        padding: 10,    // [5, 10, 15, 20] 内边距
                        position: function (p) {
                            // 位置回调
                            // console.log && console.log(p);
                            return [p[0] + 10, p[1] - 10];
                        },
                        formatter: function (params, ticket, callback) {
                            console.log(params)
                            var res = "班级" + ‘ : ‘ + params[0].name + "班<br/>";
                            for (var i = 0, l = params.length; i < l; i++) {
                                res += ‘<br/>‘ + params[i].seriesName + ‘ : ‘ + params[i].value + "<%=ViewState["unit"]%>";//鼠标悬浮显示的字符串内容
                            }
                            setTimeout(function () {
                                // 仅为了模拟异步回调
                                callback(ticket, res);
                            }, 1000)
                            return ‘loading...‘;
                        }
                        //formatter: "Template formatter: <br/>{b}<br/>{a}:{c}<br/>{a1}:{c1}"
                    },

itemStyle: { normal: {color:function (value){return \"#\"+(\"00000\"+((Math.random()*16777215+0.5)>>0).toString(16)).slice(-6); }},},