Possible to make one task appear in multiple JS task lists?

[DeutscheGabanna]

Consider this JS query:

let tasks = dv.pages(...) // fetching some tasks

// tasks[x].projects is a custom property array I add that describes which projects (1 or more) the task is assigned to (through outlinks)
for (let group of tasks.groupBy(t => t.projects)) {
	let mention_count = "mention"
		if (group.rows.length != 1) mention_count += "s"
        dv.header(4, "[[" + group.key + "]] - _" + group.rows.length + " " + mention_count + "_")
        dv.taskList(group.rows, false)
}

The problem with this query is that, if a task is assigned to more than one project, it looks like this:

How can I (in JS) attach a task in multiple such groups at once?

[blacksmithgu]

You should group by each project individually, rather than all projects. DataviewJS is missing a few utility methods to make this currently easy (I've added dv.clone() for the next release which makes this much easier), so you can do it like this in the meanwhile:

const tasks = dv.pages(...);

const groups = {};
for (let task of tasks) {
  for (let project of task.projects ?? []) {
    if (!(project in groups)) groups[project] = [task];
   else groups[project].push(task);
  }
}

for (let [project, tasks] of Object.entries(groups)) {
  dv.header(4, `[[${project}}]] - _${tasks.length} mention${tasks.length == 1 ? "" : "s"}_`);
  dv.taskList(tasks, false);
}

That may not quite compile since I didn't dry run it but it should be easy to make work.