[Question][Feature] How do you specify date format in tooltip?

What problem does this feature solve?

Please see the following sample configuration:

option = {
  dataset: {
    source: [
      { date: '3022-03-01', count: 6 },
      { date: '3022-03-02', count: 3 },
      { date: '3022-03-03', count: 4 },
      { date: '3022-03-04', count: 6 },
      { date: '3022-03-05', count: 7 },
      { date: '3022-03-06', count: 2 },
      { date: '3022-03-07', count: 8 },
      { date: '3022-03-08', count: 6 },
      { date: '3022-03-09', count: 9 }
    ]
  },
  xAxis: {
    type: 'time',
  },
  yAxis: {
    type: 'value'
  },
  series: [
    {
      type: 'line',
      name: 'Count'
    }
  ],
  tooltip: {
    trigger: 'axis'
  }
};

This results in the tooltip displaying the date with all zeros for time. Is there an easy way to format this as date-only? I know how to use a function for series.tooltip.valueFormatter for the other values, but I’m not sure how to do this for the x-axis since no series is defined for it.

What does the proposed API look like?

Perhaps a valueFormatter option added to xAxis.tooltip which accepts either a string or a function.

xAxis: {
    type: 'time',
    tooltip: {
        valueFormatter: 'yyyy-MM-dd'
    }
}

[jkasperbl]

Thanks @jiawulin001. That works, but I don’t think it’s a great solution for the following reasons:

• You have to re-apply the default tooltip styling (with series color marker, etc.) for each value displayed
• The valueFormatter functions for each series are now ignored and you have to use messier logic inside the main tooltip formatter

It would be much better if we could specify a valueFormatter for the independent axis so all other tooltip functionality works by default.

[jkasperbl]

Thanks @Airkro, that one seems to do the trick! Much appreciated!