Add active event

index.js

@@ -1,5 +1,7 @@
 'use strict';
 
+const EventEmitter = require('events');
+
 // Port of lower_bound from http://en.cppreference.com/w/cpp/algorithm/lower_bound
 // Used to compute insertion index to keep queue sorted after insertion
 function lowerBound(array, value, comp) {
@@ -51,8 +53,10 @@ class PriorityQueue {
 	}
 }
 
-class PQueue {
+class PQueue extends EventEmitter {
 	constructor(options) {
+		super();
+
 		options = Object.assign({
 			carryoverConcurrencyCount: false,
 			intervalCap: Infinity,
@@ -102,6 +106,7 @@ class PQueue {
 
 	_next() {
 		this._pendingCount--;
+		this.emit('next');
 		this._tryToStartAnother();
 	}
 

readme.md

@@ -155,6 +155,11 @@ Number of pending promises.
 
 Whether the queue is currently paused.
 
+## Events
+
+#### next
+Emitted as each item is processed in the queue for the purpose of tracking progress.
+
 ## Advanced example
 
 A more advanced example to help you understand the flow.

test.js

@@ -1,3 +1,4 @@
+import EventEmitter from 'events';
 import test from 'ava';
 import delay from 'delay';
 import inRange from 'in-range';
@@ -402,3 +403,22 @@ test('pause should work when throttled', async t => {
 	delay(2200).then(() => t.deepEqual(result, secondV));
 	await delay(2500);
 });
+
+test('should be an event emitter', t => {
+	const queue = new PQueue();
+	t.true(queue instanceof EventEmitter);
+});
+
+test('should emit next event per item', async t => {
+	const items = [0, 1, 2, 3, 4];
+	let eventCount = 0;
+	const queue = new PQueue();
+
+	queue.on('next', () => eventCount++);
+
+	items.forEach(item => queue.add(() => item));
+
+	await queue.onIdle();
+
+	t.is(eventCount, items.length);
+});