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54 lines
1.4 KiB
54 lines
1.4 KiB
4 years ago
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# parallel-transform
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[Transform stream](http://nodejs.org/api/stream.html#stream_class_stream_transform_1) for Node.js that allows you to run your transforms
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in parallel without changing the order of the output.
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npm install parallel-transform
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It is easy to use
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``` js
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var transform = require('parallel-transform');
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var stream = transform(10, function(data, callback) { // 10 is the parallism level
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setTimeout(function() {
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callback(null, data);
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}, Math.random() * 1000);
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});
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for (var i = 0; i < 10; i++) {
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stream.write(''+i);
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}
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stream.end();
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stream.on('data', function(data) {
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console.log(data); // prints 0,1,2,...
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});
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stream.on('end', function() {
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console.log('stream has ended');
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});
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```
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If you run the above example you'll notice that it runs in parallel
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(does not take ~1 second between each print) and that the order is preserved
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## Stream options
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All transforms are Node 0.10 streams. Per default they are created with the options `{objectMode:true}`.
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If you want to use your own stream options pass them as the second parameter
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``` js
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var stream = transform(10, {objectMode:false}, function(data, callback) {
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// data is now a buffer
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callback(null, data);
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});
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fs.createReadStream('filename').pipe(stream).pipe(process.stdout);
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```
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### Unordered
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Passing the option `{ordered:false}` will output the data as soon as it's processed by a transform, without waiting to respect the order.
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## License
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MIT
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