How to change xAxisTickFormatting in ngx-charts-line-chart based on timeline selection?

By default, ticks are formatted based on time range selection in timeline. If it pans across days it shows month and if it is with in a day, it shows only time. This is great!

Now I want to localize these ticks. I could provide xAxisTickFormatting to get this done but I want to have the formatting based on the time range selection. "MMM DD" or "HH:MM" based on the current time range selection.

For this I need to change the formatting function dynamically on time range selection event. Is there such an event? Or is there any other way to achieve this?

Solution

It looks like, date is formatted based on the d3 logic. It uses the precision available to that tick. So if date is 12/15/2020 11:30:00, precision is at minute level. Similarly if date is 12/15/2020 00:00:00, precision is at day level. Now we can choose the format options accordingly.

var locale = 'fr-FR'; // 'en-US'
function formatDate(value) {
  let formatOptions;
  if (value.getSeconds() !== 0) {
    formatOptions = { second: '2-digit' };
  } else if (value.getMinutes() !== 0) {
    formatOptions = { hour: '2-digit', minute: '2-digit' };
  } else if (value.getHours() !== 0) {
    formatOptions = { hour: '2-digit' };
  } else if (value.getDate() !== 1) {
    formatOptions = value.getDay() === 0 ? { month: 'short', day: '2-digit' } : { weekday: 'short', day: '2-digit' };
  } else if (value.getMonth() !== 0) {
    formatOptions = { month: 'long' };
  } else {
    formatOptions = { year: 'numeric' };
  }
  return new Intl.DateTimeFormat(locale, formatOptions).format(value);
}

var dates = ['12/15/2020 11:30:30', '12/15/2020 11:30:00', '12/15/2020 11:00:00', '12/15/2020 00:00:00', '12/13/2020 00:00:00', '12/01/2020 00:00:00', '01/01/2020 00:00:00'];
for (date of dates) {
  console.log(date, '=>', formatDate(new Date(date)));
}

Now this function can be used as

<ngx-charts-line-chart 
    [xAxis]="true" 
    [xAxisTickFormatting]="formatDate">
</ngx-charts-line-chart>