through2-promise v1.1.2
through2-promise
A small promise-based wrapper for through2, based on RangerMauve's through2-map-promise
Quickstart
npm install --save through2-promise
Some examples:
var through2 = require("through2-promise");
fs.createReadStream('ex.txt')
.pipe(through2(function (chunk) {
for (var i = 0; i < chunk.length; i++) {
if (chunk[i] == 97)
chunk[i] = 122; // swap 'a' for 'z'
this.push(chunk);
}
}))
.pipe(fs.createWriteStream('out.txt'))
.on('finish', function () {
doSomethingSpecial()
});
Or object streams:
var all = []
fs.createReadStream('data.csv')
.pipe(csv2())
.pipe(through2.obj(function (chunk) {
var data = {
name : chunk[0],
address : chunk[3],
phone : chunk[10]
};
this.push(data);
}))
.on('data', function (data) {
all.push(data)
})
.on('end', function () {
doSomethingSpecial(all)
});
API
through2-promise([options,] [fn] [, flushFunction])
Creates a transform stream which calls your transforming function, fn
. You can throw within your function to
automatically reject the promise and error-out the stream. options
is the optional object that gets passed into through2.
this
is the through2 stream, so you can do this.push()
just like in through2. If you return a Promise, and
the Promise resolves to a value, this value will be written to the stream (just like passing a value to the
callback in through2).
flushFunction()
is a function that runs after the source stream has been consumed. It has access to this.push()
,
and also any value returned will be appended to the written results.
through2-promise.obj([options,] [fn] [, flushFunction])
Same as the former, but the stream is created in objectMode.
through2-promise.ctor([options,] [fn] [, flushFunction])
Creates a constructor for your transform stream in case you want to be more efficient.