ES6 CallbackManager

A class for managing asynchronous callbacks in JavaScript

Installation

npm install es6-callback-manager --save

Note: Requires Node v4 or higher (or transformation to ES5 with Babel)

API Reference

CallbackManager

• CallbackManager
  • new CallbackManager(callback, [stopOnError])
  • .callback : function
  • .registerCallback() ⇒ function
  • .getCount() ⇒ number
  • .abort() ⇒ void

new CallbackManager(callback, [stopOnError])

Creates a new CallbackManager.

| Param | Type | Default | Description | | --- | --- | --- | --- | | callback | function | | The callback to invoke once all registered callbacks have been invoked. Is called with either null or the first Error that occurred as the first argument. | | [stopOnError] | boolean | false | If true, when an error is encountered, the callback manager aborts and immediately invokes callback. |

Example

var CallbackManager = require('es6-callback-manager');
var cbManager = new CallbackManager(function(err) {
  if (err) throw err;
  console.log('Done!');
});
setTimeout(cbManager.registerCallback(), 200);
setTimeout(cbManager.registerCallback(), 100);
setTimeout(cbManager.registerCallback(), 300);

callbackManager.callback : function

The callback passed to the constructor. Is read-only.

callbackManager.registerCallback() ⇒ function

Returns an intermediary callback and increases the number of callbacks to wait for until the original callback will be invoked.

Returns: function - An intermediary callback that, when invoked, decreases the number of callbacks to wait for. If it is the last callback being waited on, it invokes the original callback. If it is called with an Error as the first argument, the original callback will be invoked with the Error.

Example

var cbManager = new CallbackManager(callback);
process.nextTick(cbManager.registerCallback());

var cb = cbManager.registerCallback();
cb('error'); // Does nothing since a string is not an Error object

var error = new Error();
cb = cbManager.registerCallback();
cb(error); // The original callback will be called with this error

callbackManager.getCount() ⇒ number

Returns the number of intermediary callbacks currently being waited on.

Example

var cbManager = new CallbackManager(function() {
  cbManager.getCount(); // -> 0
});
process.nextTick(cbManager.registerCallback());
cbManager.getCount(); // -> 1
process.nextTick(cbManager.registerCallback());
cbManager.getCount(); // -> 2

callbackManager.abort() ⇒ void

Aborts the callback sequence, preventing the original callback from being invoked once all intermediary callbacks have been invoked.

Example

var cbManager = new CallbackManager(function() {
  console.log('This is never called');
});
setTimeout(cbManager.registerCallback(), 100);
setTimeout(function() {
  cbManager.abort();
}, 50);