Asynchronous handlers

Function factories for performing synchronous operations after asynchronous operations.

f1 = function (callback) {
  asyncOperation(function(err, result) {
    if (err) {
      callback(err);
    } else {
      callback(null, syncOperation(result);
    }
  }
}

// is equivalent to

var asyncHandlers = require('async-handlers')

f1 = function (callback) {
  handler = asyncHandlers.transform(syncOperation, callback);
  asyncOperation(handler);
}

Methods

constant(value, callback)

Returns a function with the signature (err). When called with an error, passes it to the callback. Otherwise executes callback with (null, value).

exitOnError

Returns a function with the signature (err). When called with an error, prints the error in red to stderr and exits with status 1. Otherwise does nothing.

extract(key, callback)

Returns a function with the signature (err, result). When called with an error, passes it to the callback. Otherwise executes callback with (null, result[key]).

prependToError(prefix, callback)

Returns a function with the signature (err, args...). When error is a string, prepends prefix to it if and passes it to the callback. When error is an object with a message property, prepends prefix to its message and passes it to the callback. Otherwise passes all arguments to the callback.

Note: the prefix will only be prepended if not already present.

transform(fn, callback)

Returns a function with the signature (err, result). When called with an error, passes it to the callback. Otherwise executes callback with (null, fn(result)).