Is there a way to display total quantities from events in the Scheduler Scale header, aggregated both weekly and monthly

added picture

Yes, you can use the onBeforeTimeHeaderRender event handler to customize the time header.

There is a tutorial available that shows how to calculate the summary/utilization details using methods like events.forRange(). This project displays the totals in a special frozen row but you can use the same approach with the time header.

• JavaScript Scheduler: Column Summary and Availability Chart

Thanks for the helpful explanation.
How can I determine whether the onBeforeTimeHeaderRender event is triggered for a weekly or monthly header cell? I need to apply different calculations depending on the time scale level?

The args.header.level property stores the row number (starting at 0 for the first row from the top).

You can also use args.header.start and args.header.end to get the duration:

const duration = new DayPilot.Duration(args.header.start, args.header.end);
const days = duration.totalDays();

:)

onBeforeTimeHeaderRender: (args) => {
  if (!scheduler.events.list) {
    console.log('scheduler.events.list is undefined');
    return;
  }

  if (scheduler.events.list.length === 0) {
    console.log('scheduler.events.list.length = 0');
    return;
  }

  if (args.header.level === 0 || args.header.level === 1) {
    const events = scheduler.events.forRange(args.header.start, args.header.end);
    const sum = events.reduce((acc, event) => acc + event.data.quantity, 0);
    args.header.html = `${args.header.text} ( ${sum.toString()} )`;
  }
}

Thanks for posting your solution!