80 lines
2.3 KiB
Markdown
80 lines
2.3 KiB
Markdown
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through2-filter
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===============
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[](https://nodei.co/npm/through2-filter/)
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This is a super thin wrapper around [through2](http://npm.im/through2) that works like `Array.prototype.filter` but for streams.
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For when through2 is just too verbose :wink:
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Note you will **NOT** be able to alter the content of the chunks. This is intended for filtering only. If you want to modify the stream content, use either `through2` or `through2-map`.
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```js
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var filter = require("through2-filter")
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var skip = filter(function (chunk) {
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// skip buffers longer than 100
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return chunk.length < 100
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})
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// vs. with through2:
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var skip = through2(function (chunk, encoding, callback) {
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// skip buffers longer than 100
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if (chunk.length < 100) this.push(chunk)
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return callback()
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})
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// Then use your filter:
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source.pipe(skip).pipe(sink)
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// Additionally accepts `wantStrings` argument to conver buffers into strings
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var alphanum = new RegExp("^[A-Za-z0-1]+$")
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var scrub = filter({wantStrings: true}, function (str) {
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return alphanum.exec(str)
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})
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// Works like `Array.prototype.filter` meaning you can specify a function that
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// takes up to two* arguments: fn(element, index)
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var skip10 = filter(function (element, index) {
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return index > 10
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})
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```
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*Differences from `Array.prototype.filter`:
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* No third `array` callback argument. That would require realizing the entire stream, which is generally counter-productive to stream operations.
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* `Array.prototype.filter` doesn't modify the source Array, which is somewhat nonsensical when applied to streams.
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API
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---
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`require("through2-filter")([options], fn)`
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---
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Create a `through2-filter` instance that will call `fn(chunk)`. If `fn(chunk)` returns "true" the chunk will be passed downstream. Otherwise it will be dropped.
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`require("through2-filter").ctor([options], fn)`
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---
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Create a `through2-filter` Type that can be instantiated via `new Type()` or `Type()` to create reusable spies.
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`require("through2-filter").obj([options], fn)`
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---
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Create a `through2-filter` that defaults to `objectMode = true`.
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`require("through2-filter").objCtor([options], fn)`
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---
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Create a `through2-filter` Type that defaults to `objectMode = true`.
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Options
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-------
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* wantStrings: Automatically call chunk.toString() for the super lazy.
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* all other through2 options
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LICENSE
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=======
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MIT
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