The document discusses different types of streams in Node.js including readable, writable, and transform streams. It provides code examples of creating each type of stream and processing data through them. It also discusses using streams to handle HTTP requests, error handling with streams, and debugging streams with tools like Pry and the Node.js debugger.

1. More about node.js

2. Building maintainable node.js software

3. Streams all the way down!

4. Readable Stream
var Readable = require("stream").Readable
var util = require("util")
!
function ICanRead(options) {
Readable.call(this, options)
this.data = ["I", "can", "read"]
}
util.inherits(ICanRead, Readable)
!
ICanRead.prototype._read = function(size) {
var chunk = this.data.shift()
this.push(chunk)
}
!
var rs = new ICanRead({})
!
rs.once("readable", function() {
rs.pipe(process.stdout)
})

5. Writable Stream

6. var Writable = require("stream").Writable
var util = require("util")
!
function IConcatThings(options) {
Writable.call(this, options)
this.data = []
}
util.inherits(IConcatThings, Writable)
!
IConcatThings.prototype._write = function(chunk, enc,
done) {
this.data.push(chunk)
done()
}
!
var cs = new IConcatThings({ objectMode: true })
cs.on("finish", function() {
console.log(cs.data)
})
cs.write(1)
cs.write(2)
cs.write(3)
cs.end()

7. Transform Stream

8. var Transform = require("stream").Transform
var util = require("util")
!
function ITransformThings(options) {
Transform.call(this, options)
this._writableState.objectMode = true
this._readableState.objectMode = false
}
util.inherits(ITransformThings, Transform)
!
ITransformThings.prototype._transform = function(chunk, enc,
done) {
this.push(chunk.toString())
done()
}
!
var ts = new ITransformThings()
ts.pipe(process.stdout)
ts.write(function(foo) { return foo })
ts.write("bar")
ts.write([1,2,3])
ts.end()

9. Why streams are great
function httpHandler(req, res) {
req.pipe(bodyParser)
.pipe(shortner)
.pipe(stringify)
.pipe(res)
}

10. Explicit error handling with streams
function httpHandler(req, res) {
shortner.on("error", function(err) {
res.statusCode = 500
res.end("Internal Server Error")
})
!
}
req.pipe(bodyParser)
.pipe(shortner)
.pipe(stringify)
.pipe(res)

11. Ok just a quick thing build cat!

12. Debugging… because not all code is great :(

13. Seen that before?
def my_method a
require "pry"
binding.pry
end
!
my_method "foo"

14. And this?
function myMethod(a) {
debugger
}
!
myMethod("foo")

15. using the node.js debugger