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					234 lines
				
				7.5 KiB
			
		
		
			
		
	
	
					234 lines
				
				7.5 KiB
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											4 years ago
										 
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								# asynckit [](https://www.npmjs.com/package/asynckit)
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								Minimal async jobs utility library, with streams support.
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								[](https://travis-ci.org/alexindigo/asynckit)
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								[](https://travis-ci.org/alexindigo/asynckit)
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								[](https://ci.appveyor.com/project/alexindigo/asynckit)
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								[](https://coveralls.io/github/alexindigo/asynckit?branch=master)
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								[](https://david-dm.org/alexindigo/asynckit)
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								[](https://www.bithound.io/github/alexindigo/asynckit)
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								<!-- [](https://www.npmjs.com/package/reamde) -->
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								AsyncKit provides harness for `parallel` and `serial` iterators over list of items represented by arrays or objects.
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								Optionally it accepts abort function (should be synchronously return by iterator for each item), and terminates left over jobs upon an error event. For specific iteration order built-in (`ascending` and `descending`) and custom sort helpers also supported, via `asynckit.serialOrdered` method.
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								It ensures async operations to keep behavior more stable and prevent `Maximum call stack size exceeded` errors, from sync iterators.
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								| compression        |     size |
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								| :----------------- | -------: |
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								| asynckit.js        | 12.34 kB |
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								| asynckit.min.js    |  4.11 kB |
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								| asynckit.min.js.gz |  1.47 kB |
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								## Install
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								```sh
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								$ npm install --save asynckit
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								```
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								## Examples
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								### Parallel Jobs
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								Runs iterator over provided array in parallel. Stores output in the `result` array,
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								on the matching positions. In unlikely event of an error from one of the jobs,
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								will terminate rest of the active jobs (if abort function is provided)
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								and return error along with salvaged data to the main callback function.
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								#### Input Array
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								```javascript
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								var parallel = require('asynckit').parallel
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								  , assert   = require('assert')
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								  ;
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								var source         = [ 1, 1, 4, 16, 64, 32, 8, 2 ]
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								  , expectedResult = [ 2, 2, 8, 32, 128, 64, 16, 4 ]
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								  , expectedTarget = [ 1, 1, 2, 4, 8, 16, 32, 64 ]
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								  , target         = []
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								  ;
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								parallel(source, asyncJob, function(err, result)
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								{
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								  assert.deepEqual(result, expectedResult);
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								  assert.deepEqual(target, expectedTarget);
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								});
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								// async job accepts one element from the array
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								// and a callback function
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								function asyncJob(item, cb)
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								{
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								  // different delays (in ms) per item
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								  var delay = item * 25;
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								  // pretend different jobs take different time to finish
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								  // and not in consequential order
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								  var timeoutId = setTimeout(function() {
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								    target.push(item);
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								    cb(null, item * 2);
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								  }, delay);
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								  // allow to cancel "leftover" jobs upon error
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								  // return function, invoking of which will abort this job
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								  return clearTimeout.bind(null, timeoutId);
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								}
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								```
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								More examples could be found in [test/test-parallel-array.js](test/test-parallel-array.js).
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								#### Input Object
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								Also it supports named jobs, listed via object.
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								```javascript
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								var parallel = require('asynckit/parallel')
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								  , assert   = require('assert')
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								  ;
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								var source         = { first: 1, one: 1, four: 4, sixteen: 16, sixtyFour: 64, thirtyTwo: 32, eight: 8, two: 2 }
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								  , expectedResult = { first: 2, one: 2, four: 8, sixteen: 32, sixtyFour: 128, thirtyTwo: 64, eight: 16, two: 4 }
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								  , expectedTarget = [ 1, 1, 2, 4, 8, 16, 32, 64 ]
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								  , expectedKeys   = [ 'first', 'one', 'two', 'four', 'eight', 'sixteen', 'thirtyTwo', 'sixtyFour' ]
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								  , target         = []
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								  , keys           = []
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								  ;
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								parallel(source, asyncJob, function(err, result)
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								{
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								  assert.deepEqual(result, expectedResult);
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								  assert.deepEqual(target, expectedTarget);
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								  assert.deepEqual(keys, expectedKeys);
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								});
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								// supports full value, key, callback (shortcut) interface
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								function asyncJob(item, key, cb)
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								{
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								  // different delays (in ms) per item
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								  var delay = item * 25;
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								  // pretend different jobs take different time to finish
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								  // and not in consequential order
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								  var timeoutId = setTimeout(function() {
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								    keys.push(key);
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								    target.push(item);
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								    cb(null, item * 2);
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								  }, delay);
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								  // allow to cancel "leftover" jobs upon error
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								  // return function, invoking of which will abort this job
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								  return clearTimeout.bind(null, timeoutId);
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								}
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								```
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								More examples could be found in [test/test-parallel-object.js](test/test-parallel-object.js).
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								### Serial Jobs
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								Runs iterator over provided array sequentially. Stores output in the `result` array,
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								on the matching positions. In unlikely event of an error from one of the jobs,
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								will not proceed to the rest of the items in the list
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								and return error along with salvaged data to the main callback function.
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								#### Input Array
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								```javascript
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								var serial = require('asynckit/serial')
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								  , assert = require('assert')
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								  ;
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								var source         = [ 1, 1, 4, 16, 64, 32, 8, 2 ]
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								  , expectedResult = [ 2, 2, 8, 32, 128, 64, 16, 4 ]
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								  , expectedTarget = [ 0, 1, 2, 3, 4, 5, 6, 7 ]
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								  , target         = []
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								  ;
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								serial(source, asyncJob, function(err, result)
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								{
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								  assert.deepEqual(result, expectedResult);
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								  assert.deepEqual(target, expectedTarget);
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								});
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								// extended interface (item, key, callback)
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								// also supported for arrays
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								function asyncJob(item, key, cb)
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								{
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								  target.push(key);
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								  // it will be automatically made async
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								  // even it iterator "returns" in the same event loop
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								  cb(null, item * 2);
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								}
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								```
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								More examples could be found in [test/test-serial-array.js](test/test-serial-array.js).
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								#### Input Object
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								Also it supports named jobs, listed via object.
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								```javascript
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								var serial = require('asynckit').serial
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								  , assert = require('assert')
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								  ;
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								var source         = [ 1, 1, 4, 16, 64, 32, 8, 2 ]
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								  , expectedResult = [ 2, 2, 8, 32, 128, 64, 16, 4 ]
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								  , expectedTarget = [ 0, 1, 2, 3, 4, 5, 6, 7 ]
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								  , target         = []
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								  ;
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								var source         = { first: 1, one: 1, four: 4, sixteen: 16, sixtyFour: 64, thirtyTwo: 32, eight: 8, two: 2 }
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								  , expectedResult = { first: 2, one: 2, four: 8, sixteen: 32, sixtyFour: 128, thirtyTwo: 64, eight: 16, two: 4 }
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								  , expectedTarget = [ 1, 1, 4, 16, 64, 32, 8, 2 ]
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								  , target         = []
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								  ;
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								serial(source, asyncJob, function(err, result)
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								{
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								  assert.deepEqual(result, expectedResult);
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								  assert.deepEqual(target, expectedTarget);
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								});
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								// shortcut interface (item, callback)
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								// works for object as well as for the arrays
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								function asyncJob(item, cb)
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								{
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								  target.push(item);
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								  // it will be automatically made async
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								  // even it iterator "returns" in the same event loop
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								  cb(null, item * 2);
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								}
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								```
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								More examples could be found in [test/test-serial-object.js](test/test-serial-object.js).
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								_Note: Since _object_ is an _unordered_ collection of properties,
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								it may produce unexpected results with sequential iterations.
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								Whenever order of the jobs' execution is important please use `serialOrdered` method._
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								### Ordered Serial Iterations
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								TBD
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								For example [compare-property](compare-property) package.
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								### Streaming interface
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								TBD
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								## Want to Know More?
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								More examples can be found in [test folder](test/).
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								Or open an [issue](https://github.com/alexindigo/asynckit/issues) with questions and/or suggestions.
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								## License
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								AsyncKit is licensed under the MIT license.
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