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Diffstat (limited to 'lib/tryEach.js')
-rw-r--r-- | lib/tryEach.js | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/lib/tryEach.js b/lib/tryEach.js new file mode 100644 index 0000000..d87245f --- /dev/null +++ b/lib/tryEach.js @@ -0,0 +1,58 @@ +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 + * @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(!err); + })); + }, function () { + callback(error, result); + }); +} |