echarts拖动datazoom获取起始值

dataZoom : [ 
  {
    show:true,
    xAxisIndex:[0],
    type:'slider',
    bottom:'2%',
    left:'center',
    startValue:start,
    endValue:end,
    orient:'horizontal',
    realtime:false,  //datazoom拖动完成后触发拖动事件
  },
]

let that =this
let myChartobj=that.$echarts.init(document.getElementById('dataZoomEventEchart'))
myChartobj.on( 'datazoom', function (params) {     //监听echarts的拖动事件
  that.dataZoomloading=true
  let xAxis = myChartobj.getModel().option.dataZoom[0];
  let startrang=xAxis.startValue
  let endrang=xAxis.endValue
})