accumasync

(c)Bumblehead, 2014 MIT-license

Overview:

Accumulate values asynchronously.

When looping through values in an array to perform async operations, you may be using boilerplate like this:

function collectAsync (arr, fn) {
  var newarr = [];
  (function next (x) {
    if (!x--) return fn(null, newarr);
    requestDataForElem(arr[x], function (err, res) {
      if (err) return fn(err);
      newarr.push(res);
      next(x);
    });
  }(arr.length));
}

But usually more boilerplate is necessary. The function is called frequently and to avoid exeeding stack limits a setTimeout. Some logic is added to throw an error when the given array is invalid. The order of array traversal is changed. With more boilerplate the role of the function is harder to understand.

With accumasync some of the boilerplate is removed traversal order is easily changed and an error is thrown for an invalid array. The function above becomes this:

function collectAsync (arr, fn) {
  accumasync.arr(arr, [], function (elem, index, accumarr, next) {
    requestDataForElem(elem, function (err, res) {
      if (err) return fn(err);
      accumarr.push(res);
      next(null, accumarr);
    });    
  }, fn);
}

accumasync traverses array elements, object keys and number sequences.

Methods:

accumasync methods share the same implementation and interface details. The following parameters are passed to accumulator methods:

• startvals= Array | Object | Number target element for the animation

• accumvals= * the reference to this value is passed to each callback function it may be redefined with the accumulated values

• fn= Function function is called for each item and the body of it may perform an async operation to obtain new values

  the fn function is called like this:

  fn(elem, index, accumvals, nextfn)

• exitfn= Function
  function is called at the end of traversal and may be called to prematurely end traversal

  the exitfn function is called like this:

  exitfn(err, accumvals)

accumasync.arr( arr, accum, fn, exitfn )

traverse array elements in reverse order

accumasync.arr(arr, [], function (elem, index, accumarr, next) {
  requestDataForElem(elem, function (err, res) {
    if (err) return next(err);
    accumarr.push(res);
    next(null, accumarr);
  });
}, exitfn);

accumasync.arrf( arr, accum, fn, exitfn )

traverse array elements in forward order

accumasync.arrf(arr, [], function (elem, index, accumarr, next) {
  requestDataForElem(elem, function (err, res) {
    if (err) return next(err);
    accumarr.push(res);
    next(null, accumarr);
  });
}, exitfn);

accumasync.obj( arr, accum, fn, exitfn )

traverse object keys in reverse order

accumasync.obj(obj, [], function (elem, index, accumarr, next) {
  requestDataForElem(obj[elem], function (err, res) {
    if (err) return next(err);
    accumarr.push(res);
    next(null, accumarr);
  });
}, exitfn);

accumasync.objf( arr, accum, fn, exitfn )

traverse object keys in forward order

accumasync.obj(obj, [], function (elem, index, accumarr, next) {
  requestDataForElem(obj[elem], function (err, res) {
    if (err) return next(err);
    accumarr.push(res);
    next(null, accumarr);
  });
}, exitfn);

accumasync.num( arr, accum, fn, exitfn )

traverse numbers in reverse order

accumasync.num(num, [], function (elem, index, accumarr, next) {
  requestDataForElem(num, function (err, res) {
    if (err) return next(err);
    accumarr.push(res);
    next(null, accumarr);
  });
}, exitfn);

accumasync.numf( arr, accum, fn, exitfn )

traverse numbers in forward order

accumasync.numf(num, [], function (elem, index, accumarr, next) {
  requestDataForElem(num, function (err, res) {
    if (err) return next(err);
    accumarr.push(res);
    next(null, accumarr);
  });
}, exitfn);

Install:

accumasync may be downloaded directly or installed through npm.

• npm

$ npm install accumasync

• Direct Download

$ git clone https://github.com/iambumblehead/accumasync.git

Test:

to run tests, use npm test from a shell.

$ npm test

License:

(The MIT License)

Copyright (c) 2014 Bumblehead chris@bumblehead.com

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.