A class for running multiple asynchronous functions in JavaScript. Tested in node.js, should be working in browser as well.

To run some functions asynchronously you need to create an object of the AsyncRunner class:

var ar = new AsyncRunner();

Then you can add all functions with add method.

ar.add(function(done) {
  doSomethingHere();
  done();
});

Such function gets a single callback argument, usually named done, which must be run after the function has finished. This function can provided done callback with an error (string, Error object, etc.). See below.

When all functions are added to a queue, call the run method from the ar object:

ar.run(function(err) {
  if(err) return somethingWentWrong();
  everythingWasOk();
});

The run method takes a single argument with a callback to be run after all functions were finished.

If any of functions passes an error to a done function, the callback will be run immediately and the error will be passed as an argument. All other callback would be ignored.

If any of functions will return an error the callback will be called immediately but all already running functions will run normally and won't be interrupted! Using multiple parallel asynchronous functions is recommended for receiving/fetching data only!

Simple example is shown in the examples directory. You can uncomment two lines in the middle to see how error handling works (it simulates an error on functions 5).

More examples will be added (probably).

• Simultaneous running functions count limit (with this equal to 1 it could run functions in sequence)
• Add more examples (e.g. data fetching for Express running web application)