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234 lines
7.5 KiB
Markdown
234 lines
7.5 KiB
Markdown
# 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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