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79 lines
2.3 KiB
79 lines
2.3 KiB
through2-filter |
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=============== |
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[![NPM](https://nodei.co/npm/through2-filter.png)](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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