A through2 to create an Array.prototype.map analog for streams.
This is a super thin wrapper around 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-filter. This transform also does not have a
IMPORTANT: If you return
null from your function, the stream will end there.
var map = require"through2-map"var truncate = mapreturn chunkslice0 10// vs. with through2:var truncate = through2thispushchunkslice0 10return callback// Then use your map:sourcepipetruncatepipesink// Additionally accepts `wantStrings` argument to conver buffers into stringsvar stripTags = mapwantStrings: true// OMG don't actually use thisreturn strreplace/<.*?>/g ""// Works like `Array.prototype.map` meaning you can specify a function that// takes up to two* arguments: fn(chunk, index)var spaceout = mapwantStrings: truereturn index % 2 == 0 ? chunk + "\n\n" : chunk// vs. with through2:var spaceout = through2if thisindex == thisindex = 0var buf = thisindex++ % 2 == 0 ? Bufferconcatchunk "\n\n" : chunkthispushbufreturn callback
- Cannot insert
nullelements into the stream without aborting.
- No third
arraycallback argument. That would require realizing the entire stream, which is generally counter-productive to stream operations.
Array.prototype.mapdoesn't modify the source Array, which is somewhat nonsensical when applied to streams.
stream.Transform instance that will call
fn(chunk, index) on each stream segment.
Create a reusable
stream.Transform TYPE that can be called via
new Tx or
Tx() to create an instance.
through2-map instance that defaults to
Just like ctor, but with
objectMode: true defaulting to true.
- wantStrings: Automatically call chunk.toString() for the super lazy.
- all other through2 options