Hooking into Node.js writable stream

Based on this gist. Useful when you need to test Node writable streams such as stdout.

Install

$ npm install --save-dev hook-writable-stream

Usage

Use a callback

var hookWritableStream = require('hook-writable-stream');
var hook = hookWritableStream(process.stdout, false, function(string) {
  //=> string === 'hooked!\n'
});

console.log('hooked!');
hook.unhook();
console.log('unhooked!');
//=> 'unhooked!' is shown on your console

Use as a stream

var hookWritableStream = require('hook-writable-stream');
var through = require('through2');

var hook = hookWritableStream(process.stdout, false);
var stream = hook.stream;
stream.pipe(through(function(chunk, enc, cb) {
  //=> chunk.toString() === 'hooked!\n'
  cb(chunk);
}));

console.log('hooked!');
hook.unhook();
console.log('unhooked!');
//=> 'unhooked!' is shown on your console

API

hookWritableStream(writableStream, [keepOriginal], [callback])

Returns an object.

unhook

Type: function

Call to unhook the writable stream.

stream

A stream that you can consume. The data that was going to written to the original stream is written to this stream.

writableStream

A node writable stream such as process.stdout.

keepOriginal

true to keep writing to the original stream.

callback(obj)

obj

Whatever is written to the original stream.

License

MIT © Steve Mao