through-pipes

Create a through stream that wraps/nests a number of pipe statements.

Install

Install with npm.

npm install --save-dev through-pipes

Usage

The primary use case is where you wish to define a subroutine that is to be used in a pipe statement. However in this subroutine you would also like to pipe through a set of streams.

The following example encapsulates a pre-minify and ugilfy as a minify subroutine for Gulp.

var through = require('through-pipes');
var ngmin = require('gulp-ngmin');
var uglify = require('gulp-uglify');
 
function minify() {
  return through(function(readable) {
    return readable
      .pipe(ngmin())
      .pipe(uglify())
  }
}
 
var gulp = require('gulp');
 
gulp.task('default', function() {
  gulp.src('js/**/*.js')
    .pipe(minify())
    .pipe(gulp.dest('dist'))
});

Note that minification is an arbitrary and somewhat inappropriate example. You would normally be implementing something more specific that would be contained in a separate node package.

Other than the top-level factory method, there are a number of other methods that may be used to push input explicitly to the subroutine.

The following example pushes 3 files, and a stream end event, directly to the readable stream.

var through = require('through-pipes');
var ngmin = require('gulp-ngmin');
var uglify = require('gulp-uglify');

through(function(readable) {
  return readable
    .pipe(ngmin())
    .pipe(uglify())
})
.output(function(file) {
  /* do something with each minified file */
})
.done(function() {
  /* do something at the end */
})
.input(fileA, fileB, fileC)
.end();

Limitations

Suitable for object streams only.

Reference

(method)

Creates a new instance.

@param {function(stream.Readable):stream.Readable} method A factory method that returns a stream

@returns {stream.Through} A through stream that wraps the pipe

.input(...)

Bypass the through stream and directly push values to the internal input stream.

@param {...object} Any number of objects to add to the input.

@returns {stream.Through} The through stream on which the method was called.

.end()

Bypass the through stream and directly push null to the internal input stream to trigger end.

@returns {stream.Through} The through stream on which the method was called.

.output(method)

A convenience for .on('data', method).

@param {function(string, function)} method The method to be called on the data event.

@returns {stream.Through} The through stream on which the method was called.

.done(method)

A convenience for .on('end', method).

@param {function(string, function)} method The method to be called on the end event.

@returns {stream.Through} The through stream on which the method was called.