notify-queue

A Queue with a callback driven pop(). push() and pop() are relatively normal, but pop() instead takes a callback and is called whenever there is an item available.

It's ideal for creating a work-queue where each worker needs to process one item at a time and should be notified when new items are added.

Example Usage

Simplest usage:

var NotifyQueue = require('notify-queue');
var q = new NotifyQueue();
 
q.pop(function(item) {
   // do some stuff with item.
});
 
q.push("an item");

Simplest usage:

var NotifyQueue = require('notify-queue');
var q = new NotifyQueue();
 
var cancel = q.pop(function(item) {
   // do some stuff with item.
});
 
cancel();
 
q.push("an item"); // the callback above won't be called

One pop() call can be called multiple times if next() is used:

var NotifyQueue = require('notify-queue');
var q = new NotifyQueue();
 
q.pop(function(item, next) {
   someasyncfunction(item, function() {
      next();
   });
});
 
q.push("an item");
q.push("another item");

Or, with matchers:

var NotifyQueue = require('notify-queue');
var q = new NotifyQueue();
 
function processor(item) {
   // only called when item.isForMe == true
});
 
function matcher(item) {
  return item.isForMe == true;
}
 
q.pop(processor, matcher)
 
q.push("an item");
q.push({isForMe: true, msg: "an item"});

Interface

queue.push(item)

Adds an item to the queue triggering any waiting pop() callbacks.

queue.pop(callback[, matcher])

Registers callback so it's called whenever an item is added to the queue. If a matcher function is provided, callback will only be called when matcher(item) returns something truthy. Otherwise, callback will be called for the first item.

callback is passed the item and a next() function. callback will not be called again unless next() is called. If pop() is called more than once, available callbacks will be served items in a round-robin fashion. An available callback is one that is not waiting for next() to be called.

pop() returns a function that when called, removes the callback from the list of waiting callbacks and ensures it will not be called again.

queue.items()

Returns the array of items currently in the queue. This is the internal representation and can be modified as necessary to remove or rearrange items.