4.0.0 • Published 6 months ago
through2-filter v4.0.0
through2-filter
This is a super thin wrapper around through2 that works like Array.prototype.filter
but for streams.
For when through2 is just too verbose :wink:
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
.
var filter = require("through2-filter")
var skip = filter(function (chunk) {
// skip buffers longer than 100
return chunk.length < 100
})
// vs. with through2:
var skip = through2(function (chunk, encoding, callback) {
// skip buffers longer than 100
if (chunk.length < 100) this.push(chunk)
return callback()
})
// Then use your filter:
source.pipe(skip).pipe(sink)
// Additionally accepts `wantStrings` argument to conver buffers into strings
var alphanum = new RegExp("^[A-Za-z0-1]+$")
var scrub = filter({wantStrings: true}, function (str) {
return alphanum.exec(str)
})
// Works like `Array.prototype.filter` meaning you can specify a function that
// takes up to two* arguments: fn(element, index)
var skip10 = filter(function (element, index) {
return index > 10
})
*Differences from Array.prototype.filter
:
- No third
array
callback argument. That would require realizing the entire stream, which is generally counter-productive to stream operations. Array.prototype.filter
doesn't modify the source Array, which is somewhat nonsensical when applied to streams.
API
require("through2-filter")([options], fn)
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.
require("through2-filter").ctor([options], fn)
Create a through2-filter
Type that can be instantiated via new Type()
or Type()
to create reusable spies.
require("through2-filter").obj([options], fn)
Create a through2-filter
that defaults to objectMode = true
.
require("through2-filter").objCtor([options], fn)
Create a through2-filter
Type that defaults to objectMode = true
.
Options
- wantStrings: Automatically call chunk.toString() for the super lazy.
- all other through2 options
LICENSE
MIT