Current File : //opt/alt/alt-nodejs11/root/lib/node_modules/npm/node_modules.bundled/through/readme.markdown
#through
[](http://travis-ci.org/dominictarr/through)
[](https://ci.testling.com/dominictarr/through)
Easy way to create a `Stream` that is both `readable` and `writable`.
* Pass in optional `write` and `end` methods.
* `through` takes care of pause/resume logic if you use `this.queue(data)` instead of `this.emit('data', data)`.
* Use `this.pause()` and `this.resume()` to manage flow.
* Check `this.paused` to see current flow state. (`write` always returns `!this.paused`).
This function is the basis for most of the synchronous streams in
[event-stream](http://github.com/dominictarr/event-stream).
``` js
var through = require('through')
through(function write(data) {
this.queue(data) //data *must* not be null
},
function end () { //optional
this.queue(null)
})
```
Or, can also be used _without_ buffering on pause, use `this.emit('data', data)`,
and this.emit('end')
``` js
var through = require('through')
through(function write(data) {
this.emit('data', data)
//this.pause()
},
function end () { //optional
this.emit('end')
})
```
## Extended Options
You will probably not need these 99% of the time.
### autoDestroy=false
By default, `through` emits close when the writable
and readable side of the stream has ended.
If that is not desired, set `autoDestroy=false`.
``` js
var through = require('through')
//like this
var ts = through(write, end, {autoDestroy: false})
//or like this
var ts = through(write, end)
ts.autoDestroy = false
```
## License
MIT / Apache2
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