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Track complex hiearchies of asynchronous task completion statuses. This is intended to give you a way of recording and reporting the progress of the big recursive fan-out and gather type workflows that are so common in async.

What you do with this completion data is up to you, but the most common use case is to feed it to one of the many progress bar modules.

Most progress bar modules include a rudamentary version of this, but my needs were more complex.


var TrackerGroup = require("are-we-there-yet").TrackerGroup

var top = new TrackerGroup("program")

var single = top.newItem("one thing", 100)

console.log(top.completed()) // 0.2

fs.stat("file", function(er, stat) {
  if (er) throw er  
  var stream = top.newStream("file", stat.size)
  console.log(top.completed()) // now 0.1 as single is 50% of the job and is 20% complete
                              // and 50% * 20% == 10%
  fs.createReadStream("file").pipe(stream).on("data", function (chunk) {
    // do stuff with chunk
  top.on("change", function (name) {
    // called each time a chunk is read from "file"
    // top.completed() will start at 0.1 and fill up to 0.6 as the file is read

Shared Methods

Implemented in: Tracker, TrackerGroup, TrackerStream

Returns the ratio of completed work to work to be done. Range of 0 to 1.

Implemented in: Tracker, TrackerGroup

Marks the tracker as completed. With a TrackerGroup this marks all of its components as completed.

Marks all of the components of this tracker as finished, which in turn means that tracker.completed() for this will now be 1.

This will result in one or more change events being emitted.


All tracker objects emit change events with the following arguments:

function (name, completed, tracker)

name is the name of the tracker that originally emitted the event, or if it didn’t have one, the first containing tracker group that had one.

completed is the percent complete (as returned by tracker.completed() method).

tracker is the tracker object that you are listening for events on.


Creates a new empty tracker aggregation group. These are trackers whose completion status is determined by the completion status of other trackers.

Adds the otherTracker to this aggregation group. The weight determines how long you expect this tracker to take to complete in proportion to other units. So for instance, if you add one tracker with a weight of 1 and another with a weight of 2, you’re saying the second will take twice as long to complete as the first. As such, the first will account for 33% of the completion of this tracker and the second will account for the other 67%.

Returns otherTracker.

The above is exactly equivalent to:

  var subGroup = tracker.addUnit(new TrackerGroup(name), weight)

The above is exactly equivalent to:

  var subItem = tracker.addUnit(new Tracker(name, todo), weight)

The above is exactly equivalent to:

  var subStream = tracker.addUnit(new TrackerStream(name, todo), weight)

Returns a tree showing the completion of this tracker group and all of its children, including recursively entering all of the children.


Ordinarily these are constructed as a part of a tracker group (via newItem).

Returns the ratio of completed work to work to be done. Range of 0 to 1. If total work to be done is 0 then it will return 0.

Increases the amount of work to be done, thus decreasing the completion percentage. Triggers a change event.

Increase the amount of work complete, thus increasing the completion percentage. Will never increase the work completed past the amount of work todo. That is, percentages > 100% are not allowed. Triggers a change event.

Marks this tracker as finished, tracker.completed() will now be 1. Triggers a change event.


The tracker stream object is a pass through stream that updates an internal tracker object each time a block passes through. It’s intended to track downloads, file extraction and other related activities. You use it by piping your data source into it and then using it as your data source.

If your data has a length attribute then that’s used as the amount of work completed when the chunk is passed through. If it does not (eg, object streams) then each chunk counts as completing 1 unit of work, so your size should be the total number of objects being streamed.

Increases the amount of work to be done, thus decreasing the completion percentage. Triggers a change event.