Adding a callback to change the value of context.parsed.x in the tooltip

[o-alquimista]

In this example, you can see it is changing the value of context.parsed.y.

var chart = new Chart(ctx, {
    type: 'line',
    data: data,
    options: {
        plugins: {
            tooltip: {
                callbacks: {
                    label: function(context) {
                        var label = context.dataset.label || '';

                        if (label) {
                            label += ': ';
                        }
                        if (context.parsed.y !== null) {
                            label += new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' }).format(context.parsed.y);
                        }
                        return label;
                    }
                }
            }
        }
    }
});

I also want to change the value of context.parsed.x, but since the callback above is already returning a value, I'm a little confused as to how to accomplish that. Help? :)

You can see in this screenshot that I have already applied a format to the ticks in the x axis. The tooltip, however, is still showing the unformatted string (e.g. 2020-06). It needs to display 06/2020 instead.

Details

Chart.js version 3.5.1

[LeeLenaleee]

You need to use the title callback: https://jsfiddle.net/Leelenaleee/jrfcoa6v/3/

[o-alquimista]

It works, thank you.

docs reference

But it's a little weird that you have to access the value by index: tootipItem[0].label. Isn't there a cleaner way? For example, here I'm using this.getLabelForValue(value):

x: {
  ticks: {
    callback: function(value, index, values) {
      let [year, month] = this.getLabelForValue(value).split('-');
      month = month.padStart(2, '0');
      let date = `${month}/${year`;

      return date;
    }
  }
}

[LeeLenaleee]

No because for the default mode it only gives you 1 tick back but if you set the mode to dataset for example you get an array back containing all the ticks as you can see here: https://jsfiddle.net/Leelenaleee/jrfcoa6v/4/