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import eachOf from './eachOf.js'
import _parallel from './internal/parallel.js'
/**
* Run the `tasks` collection of functions in parallel, without waiting until
* the previous function has completed. If any of the functions pass an error to
* its callback, the main `callback` is immediately called with the value of the
* error. Once the `tasks` have completed, the results are passed to the final
* `callback` as an array.
*
* **Note:** `parallel` is about kicking-off I/O tasks in parallel, not about
* parallel execution of code. If your tasks do not use any timers or perform
* any I/O, they will actually be executed in series. Any synchronous setup
* sections for each task will happen one after the other. JavaScript remains
* single-threaded.
*
* **Hint:** Use [`reflect`]{@link module:Utils.reflect} to continue the
* execution of other tasks when a task fails.
*
* It is also possible to use an object instead of an array. Each property will
* be run as a function and the results will be passed to the final `callback`
* as an object instead of an array. This can be a more readable way of handling
* results from {@link async.parallel}.
*
* @name parallel
* @static
* @memberOf module:ControlFlow
* @method
* @category Control Flow
* @param {Array|Iterable|AsyncIterable|Object} tasks - A collection of
* [async functions]{@link AsyncFunction} to run.
* Each async function can complete with any number of optional `result` values.
* @param {Function} [callback] - An optional callback to run once all the
* functions have completed successfully. This function gets a results array
* (or object) containing all the result arguments passed to the task callbacks.
* Invoked with (err, results).
* @returns {Promise} a promise, if a callback is not passed
*
* @example
*
* //Using Callbacks
* async.parallel([
* function(callback) {
* setTimeout(function() {
* callback(null, 'one');
* }, 200);
* },
* function(callback) {
* setTimeout(function() {
* callback(null, 'two');
* }, 100);
* }
* ], function(err, results) {
* console.log(results);
* // results is equal to ['one','two'] even though
* // the second function had a shorter timeout.
* });
*
* // an example using an object instead of an array
* async.parallel({
* one: function(callback) {
* setTimeout(function() {
* callback(null, 1);
* }, 200);
* },
* two: function(callback) {
* setTimeout(function() {
* callback(null, 2);
* }, 100);
* }
* }, function(err, results) {
* console.log(results);
* // results is equal to: { one: 1, two: 2 }
* });
*
* //Using Promises
* async.parallel([
* function(callback) {
* setTimeout(function() {
* callback(null, 'one');
* }, 200);
* },
* function(callback) {
* setTimeout(function() {
* callback(null, 'two');
* }, 100);
* }
* ]).then(results => {
* console.log(results);
* // results is equal to ['one','two'] even though
* // the second function had a shorter timeout.
* }).catch(err => {
* console.log(err);
* });
*
* // an example using an object instead of an array
* async.parallel({
* one: function(callback) {
* setTimeout(function() {
* callback(null, 1);
* }, 200);
* },
* two: function(callback) {
* setTimeout(function() {
* callback(null, 2);
* }, 100);
* }
* }).then(results => {
* console.log(results);
* // results is equal to: { one: 1, two: 2 }
* }).catch(err => {
* console.log(err);
* });
*
* //Using async/await
* async () => {
* try {
* let results = await async.parallel([
* function(callback) {
* setTimeout(function() {
* callback(null, 'one');
* }, 200);
* },
* function(callback) {
* setTimeout(function() {
* callback(null, 'two');
* }, 100);
* }
* ]);
* console.log(results);
* // results is equal to ['one','two'] even though
* // the second function had a shorter timeout.
* }
* catch (err) {
* console.log(err);
* }
* }
*
* // an example using an object instead of an array
* async () => {
* try {
* let results = await async.parallel({
* one: function(callback) {
* setTimeout(function() {
* callback(null, 1);
* }, 200);
* },
* two: function(callback) {
* setTimeout(function() {
* callback(null, 2);
* }, 100);
* }
* });
* console.log(results);
* // results is equal to: { one: 1, two: 2 }
* }
* catch (err) {
* console.log(err);
* }
* }
*
*/
export default function parallel(tasks, callback) {
return _parallel(eachOf, tasks, callback);
}
|
