bar中tooltip的valueFormatter为啥无效

[lumingyuan]

{
  name: 'ga',
  type: 'bar',
  showBackground: true,
  backgroundStyle: {
    borderRadius: [5, 5, 0, 0]
  },
  tooltip: {
    valueFormatter: (value) => '$' + value.toFixed(2)
  },
  itemStyle: {
    borderRadius: [5, 5, 0, 0]
  },
  data: [
    0, 36.93000000000029, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0
  ]
}

tooltip里的valueFormatter和formatter设置后都无效果