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