https://github.com/brycebaril/through2-map
A through2 to create an Array.prototype.map analog for streams.
https://github.com/brycebaril/through2-map
Last synced: about 1 year ago
JSON representation
A through2 to create an Array.prototype.map analog for streams.
- Host: GitHub
- URL: https://github.com/brycebaril/through2-map
- Owner: brycebaril
- License: mit
- Created: 2013-08-06T05:11:29.000Z (over 12 years ago)
- Default Branch: master
- Last Pushed: 2024-04-13T01:06:55.000Z (about 2 years ago)
- Last Synced: 2024-04-14T18:08:00.590Z (almost 2 years ago)
- Language: JavaScript
- Size: 18.6 KB
- Stars: 70
- Watchers: 3
- Forks: 2
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
through2-map
============
[](https://nodei.co/npm/through2-map/)
This is a super thin wrapper around [through2](http://npm.im/through2) that works like `Array.prototype.map` but for streams.
For when through2 is just too verbose :wink:
Note you will **NOT** be able to skip chunks. This is intended for modification only. If you want filter the stream content, use either `through2` or `through2-filter`. This transform also does not have a `flush` function.
**IMPORTANT:** If you return `null` from your function, the stream will end there.
```js
var map = require("through2-map")
var truncate = map(function (chunk) {
return chunk.slice(0, 10)
})
// vs. with through2:
var truncate = through2(function (chunk, encoding, callback) {
this.push(chunk.slice(0, 10))
return callback()
})
// Then use your map:
source.pipe(truncate).pipe(sink)
// Additionally accepts `wantStrings` argument to convert buffers into strings
var stripTags = map({wantStrings: true}, function (str) {
// OMG don't actually use this
return str.replace(/<.*?>/g, "")
})
// Works like `Array.prototype.map` meaning you can specify a function that
// takes up to two* arguments: fn(chunk, index)
var spaceout = map({wantStrings: true}, function (chunk, index) {
return (index % 2 == 0) ? chunk + "\n\n" : chunk
})
// vs. with through2:
var spaceout = through2(function (chunk, encoding, callback) {
if (this.index == undefined) this.index = 0
var buf = (this.index++ % 2 == 0) ? Buffer.concat(chunk, new Buffer("\n\n")) : chunk
this.push(buf)
return callback()
})
```
*Differences from `Array.prototype.map`:
* Cannot insert `null` elements into the stream without aborting.
* No third `array` callback argument. That would require realizing the entire stream, which is generally counter-productive to stream operations.
* `Array.prototype.map` doesn't modify the source Array, which is somewhat nonsensical when applied to streams.
API
---
```
require("through2-map")([options,] fn)
```
Create a `stream.Transform` instance that will call `fn(chunk, index)` on each stream segment.
- - -
```
var Tx = require("through2-map").ctor([options,] fn)
```
Create a reusable `stream.Transform` TYPE that can be called via `new Tx` or `Tx()` to create an instance.
- - -
```
require("through2-map").obj([options,] fn)
```
Create a `through2-map` instance that defaults to `objectMode: true`.
- - -
```
require("through2-map").objCtor([options,] fn)
```
Just like ctor, but with `objectMode: true` defaulting to true.
Options
-------
* wantStrings: Automatically call chunk.toString() for the super lazy.
* all other through2 options
LICENSE
=======
MIT