Controller of consecutive or concurrent execution of a sequence of asynchronous operations

Example

var AsyncCtrl = require("async-ctrl");
var initialValue = 1;
var scopeObject = {};
AsyncCtrl([
    function(success, failure, value, scope) {
        setTimeout(function() { 
            success(value * 2);
        }, 1500);
    },
    [function(success, failure, value, scope) {
        setTimeout(function() { 
            if ( ++scope.successes$ === 2 )
                success(value * 3);
        }, 2500);
    }, function(success, failure, value, scope) {
        setTimeout(function() { 
            if ( ++scope.successes$ === 2 )
                success(value * 2);
        }, 1500);
    }, function(success, failure, value, scope) {
        setTimeout(function() { 
            failure(-value);
        }, 3500);
    }],
])(initialValue, scopeObject)
    .onSuccess(function(value) {
        console.log(value); //6
    })
    .onFailure(function(error) {
        console.error(error);
    });

Usage

The first step is defining the task list. The entry point function (AsyncCtrl) accepts this list and return controller's constructor for this list and its invocation starts the execution. That constructor accepts two optional arguments: initial value for the first task and object meant to imitate the inner scope of the tasks. The constructor returns controller's instance with onSuccess(handler) and onFailure(handler) methods for assigning the execution outcome handlers. The fact of the handlers' invocations is independent of the time they were assigned. It is possible to terminate the further execution by calling the failure(error) method of the instance in which case the failure handlers will be invoked. Ultimately only one group of handlers will be triggered.

Convention

The list of tasks is an array containing consecutively executed tasks. Each of these tasks is a function or an array of functions being invoked simultaneously. Successfulness is reported via the first argument of the function and an error via the second one. For each task only the first such report takes effect. Once a successful result is reported the execution process proceeds to the next task or is terminated in case of an error. Each function receives the successful result of the previous task via the third argument and the scope object via the fourth argument. Before the execution of the next task begins the attribute values$ of the scope object is assigned to an empty array and the attributes successes$ and failures$ are assigned to a value 0 which enables communications between concurrently executed functions. The last task's successful result or an error report will be passed to the appropriate outcome handlers.