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135 lines
3.5 KiB
Markdown
135 lines
3.5 KiB
Markdown
# unique-stream
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node.js through stream that emits a unique stream of objects based on criteria
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[](https://travis-ci.org/eugeneware/unique-stream)
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[](https://coveralls.io/github/eugeneware/unique-stream?branch=master)
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## Installation
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Install via [npm](https://www.npmjs.com/):
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```
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$ npm install unique-stream
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```
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## Examples
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### Dedupe a ReadStream based on JSON.stringify:
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``` js
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var unique = require('unique-stream')
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, Stream = require('stream');
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// return a stream of 3 identical objects
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function makeStreamOfObjects() {
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var s = new Stream;
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s.readable = true;
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var count = 3;
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for (var i = 0; i < 3; i++) {
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setImmediate(function () {
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s.emit('data', { name: 'Bob', number: 123 });
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--count || end();
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});
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}
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function end() {
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s.emit('end');
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}
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return s;
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}
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// Will only print out one object as the rest are dupes. (Uses JSON.stringify)
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makeStreamOfObjects()
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.pipe(unique())
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.on('data', console.log);
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```
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### Dedupe a ReadStream based on an object property:
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``` js
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// Use name as the key field to dedupe on. Will only print one object
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makeStreamOfObjects()
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.pipe(unique('name'))
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.on('data', console.log);
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```
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### Dedupe a ReadStream based on a custom function:
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``` js
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// Use a custom function to dedupe on. Use the 'number' field. Will only print one object.
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makeStreamOfObjects()
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.pipe(function (data) {
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return data.number;
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})
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.on('data', console.log);
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```
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## Dedupe multiple streams
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The reason I wrote this was to dedupe multiple object streams:
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``` js
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var aggregator = unique();
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// Stream 1
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makeStreamOfObjects()
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.pipe(aggregator);
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// Stream 2
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makeStreamOfObjects()
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.pipe(aggregator);
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// Stream 3
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makeStreamOfObjects()
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.pipe(aggregator);
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aggregator.on('data', console.log);
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```
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## Use a custom store to record keys that have been encountered
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By default a set is used to store keys encountered so far, in order to check new ones for
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uniqueness. You can supply your own store instead, providing it supports the add(key) and
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has(key) methods. This could allow you to use a persistent store so that already encountered
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objects are not re-streamed when node is reloaded.
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``` js
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var keyStore = {
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store: {},
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add: function(key) {
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this.store[key] = true;
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},
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has: function(key) {
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return this.store[key] !== undefined;
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}
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};
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makeStreamOfObjects()
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.pipe(unique('name', keyStore))
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.on('data', console.log);
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```
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## Contributing
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unique-stream is an **OPEN Open Source Project**. This means that:
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> Individuals making significant and valuable contributions are given commit-access to the project to contribute as they see fit. This project is more like an open wiki than a standard guarded open source project.
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See the [CONTRIBUTING.md](https://github.com/eugeneware/unique-stream/blob/master/CONTRIBUTING.md) file for more details.
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### Contributors
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unique-stream is only possible due to the excellent work of the following contributors:
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<table><tbody>
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<tr><th align="left">Eugene Ware</th><td><a href="https://github.com/eugeneware">GitHub/eugeneware</a></td></tr>
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<tr><th align="left">Craig Ambrose</th><td><a href="https://github.com/craigambrose">GitHub/craigambrose</a></td></tr>
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<tr><th align="left">Shinnosuke Watanabe</th><td><a href="https://github.com/shinnn">GitHub/shinnn</a></td></tr>
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<tr><th align="left">Rouven Weßling</th><td><a href="https://github.com/realityking">GitHub/realityking</a></td></tr>
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</tbody></table>
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