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https://github.com/thlorenz/async-through
Readable stream that ensures that onend is only called once no ondata items are pending, thus supporting async operations inside ondata.
https://github.com/thlorenz/async-through
Last synced: 26 days ago
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Readable stream that ensures that onend is only called once no ondata items are pending, thus supporting async operations inside ondata.
- Host: GitHub
- URL: https://github.com/thlorenz/async-through
- Owner: thlorenz
- License: mit
- Created: 2013-08-17T15:36:02.000Z (over 11 years ago)
- Default Branch: master
- Last Pushed: 2013-08-18T15:46:14.000Z (over 11 years ago)
- Last Synced: 2024-12-02T02:04:22.924Z (about 1 month ago)
- Language: JavaScript
- Homepage:
- Size: 97.7 KB
- Stars: 1
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# async-through [](http://travis-ci.org/thlorenz/async-through)
[](https://ci.testling.com/thlorenz/async-through)
Readable stream that ensures that onend is only called once no ondata items are pending, thus supporting async operations inside ondata.
```js
var asyncThru = require('async-through')
var from = require('from');
var stream = asyncThru(ondata, onend);
function ondata(data) {
setTimeout(function () {
stream.queue(data * 2 + '\n');
// this === stream, so the below also works:
// this.queue(data * 2 + '\n');
}, 200 * data);
}
function onend() {
// this === stream, so the below also works:
// this.queue(null);
stream.queue(null);
}
from([1, 3, 4, 5])
.pipe(stream)
.on('end', function () { console.log('stream ended'); })
.pipe(process.stdout);
```
```
2
6
8
10
stream ended
```
#### `onend` is optional
```js
var from = require('from');
// onend is optional
var stream = asyncThru(ondata);
function ondata(data) {
setTimeout(function () {
stream.queue(data * 2 + '\n');
}, 200 * data);
}
from([1, 3, 4, 5])
.pipe(stream)
.on('end', function () { console.log('stream ended'); })
.pipe(process.stdout);
```
#### one to many
```js
var stream = asyncThru(ondata);
function ondata(data) {
setTimeout(function () {
stream.queue(data * 2 + '\n', true);
stream.queue(data / 2 + '\n');
}, 200 * data);
}
from([1, 2, 3])
.pipe(stream)
.on('end', function () { console.log('stream ended'); })
.pipe(process.stdout);
```
```
2
0.5
4
1
6
1.5
stream ended
```
## Installation
npm install async-through
## API
### *asyncThrough(ondata, onend)*
```
/**
* Returns a stream that works just like a normal through stream except that it keeps track of pending items that are
* being processed inside the `ondata` function.
* This allows the processing code to be async yet ensures that `onend` doesn't get called until no items are pending.
*
* @name exports
* @function
* @param ondata_ {Function} function (data) { .. } to process data item and queue the result
* @param onend_ {Function} (optional) function () { .. }
* @return {Stream} async-through stream
*/
```
### one-to-many
If you want to `queue` multiple results per incoming item, do so by providing `true` as the second paramater to `queue`
in order to signal that more results for this item are coming.
```js
stream.queue(fst, true);
stream.queue(snd, true);
stream.queue(trd, true);
stream.queue(last);
```
## License
MIT