diff --git a/lib/index.js b/lib/index.js index 8a2c7cad9..678b9e6ff 100644 --- a/lib/index.js +++ b/lib/index.js @@ -89,6 +89,7 @@ import times from './times'; import timesLimit from './timesLimit'; import timesSeries from './timesSeries'; import transform from './transform'; +import tryEach from './tryEach'; import unmemoize from './unmemoize'; import until from './until'; import waterfall from './waterfall'; @@ -163,6 +164,7 @@ export default { timesLimit: timesLimit, timesSeries: timesSeries, transform: transform, + tryEach: tryEach, unmemoize: unmemoize, until: until, waterfall: waterfall, @@ -255,6 +257,7 @@ export { timesLimit as timesLimit, timesSeries as timesSeries, transform as transform, + tryEach as tryEach, unmemoize as unmemoize, until as until, waterfall as waterfall, diff --git a/lib/tryEach.js b/lib/tryEach.js new file mode 100644 index 000000000..51f561307 --- /dev/null +++ b/lib/tryEach.js @@ -0,0 +1,63 @@ +import noop from 'lodash/noop'; +import eachSeries from './eachSeries'; +import rest from './internal/rest'; + +/** + * It runs each task in series but stops whenever any of the functions were + * successful. If one of the tasks were successful, the `callback` will be + * passed the result of the successful task. If all tasks fail, the callback + * will be passed the error and result (if any) of the final attempt. + * + * @name tryEach + * @static + * @memberOf module:ControlFlow + * @method + * @category Control Flow + * @name series + * @static + * @memberOf module:ControlFlow + * @method + * @category Control Flow + * @param {Array|Iterable|Object} tasks - A collection containing functions to + * run, each function is passed a `callback(err, result)` it must call on + * completion with an error `err` (which can be `null`) and an optional `result` + * value. + * @param {Function} [callback] - An optional callback which is called when one + * of the tasks has succeeded, or all have failed. It receives the `err` and + * `result` arguments of the last attempt at completing the `task`. Invoked with + * (err, results). + * @example + * async.try([ + * function getDataFromFirstWebsite(callback) { + * // Try getting the data from the first website + * callback(err, data); + * }, + * function getDataFromSecondWebsite(callback) { + * // First website failed, + * // Try getting the data from the backup website + * callback(err, data); + * } + * ], + * // optional callback + * function(err, results) { + * Now do something with the data. + * }); + * + */ +export default function tryEach(tasks, callback) { + var error = null; + var result; + callback = callback || noop; + eachSeries(tasks, function(task, callback) { + task(rest(function (err, args) { + if (args.length <= 1) { + args = args[0]; + } + error = err; + result = args; + callback(args); + })); + }, function () { + callback(error, result); + }); +} diff --git a/mocha_test/tryEach.js b/mocha_test/tryEach.js new file mode 100644 index 000000000..f97c3ce0b --- /dev/null +++ b/mocha_test/tryEach.js @@ -0,0 +1,86 @@ +var async = require('../lib'); +var expect = require('chai').expect; +var assert = require('assert'); + +describe('try', function () { + it('no callback', function () { + async.tryEach([]); + }); + it('empty', function (done) { + async.tryEach([], function (err, results) { + expect(err).to.equal(null); + expect(results).to.eql(undefined); + done(); + }); + }); + it('one task, multiple results', function (done) { + var RESULTS = ['something', 'something2']; + async.tryEach([ + function (callback) { + callback(null, RESULTS[0], RESULTS[1]); + } + ], function (err, results) { + expect(err).to.equal(null); + expect(results).to.eql(RESULTS); + done(); + }); + }); + it('one task', function (done) { + var RESULT = 'something'; + async.tryEach([ + function (callback) { + callback(null, RESULT); + } + ], function (err, results) { + expect(err).to.equal(null); + expect(results).to.eql(RESULT); + done(); + }); + }); + it('two tasks, one failing', function (done) { + var RESULT = 'something'; + async.tryEach([ + function (callback) { + callback(new Error('Failure')); + }, + function (callback) { + callback(null, RESULT); + } + ], function (err, results) { + expect(err).to.equal(null); + expect(results).to.eql(RESULT); + done(); + }); + }); + it('two tasks, both failing', function (done) { + var ERROR_RESULT = new Error('Failure2'); + async.tryEach([ + function (callback) { + callback(new Error('Should not stop here')); + }, + function (callback) { + callback(ERROR_RESULT); + } + ], function (err, results) { + expect(err).to.equal(ERROR_RESULT); + expect(results).to.eql(undefined); + done(); + }); + }); + it('two tasks, non failing', function (done) { + var RESULT = 'something'; + async.tryEach([ + function (callback) { + callback(null, RESULT); + }, + function () { + assert.fail('Should not been called'); + }, + ], function (err, results) { + expect(err).to.equal(null); + expect(results).to.eql(RESULT); + done(); + }); + }); +}); +