Class 04 Node Architecture, Asynchronous, Events

Questions and Feedback

* file system command are relative to cwd (pwd)
* not the same as require which is relative to the file in which it appears
* mocha -w hangs on some errors
* nodemon
* ?

Learning Objectives

* Have a working model of asynchronous programming in NodeJS
* Utilize events and event emitters

Agenda

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* What is it?
* Node Event Loop
* Basic node architecture 101
* v8 + event-loop + os-lib
* Thread - actual "thread of execution"
* Event loop explained
* JavaScript single threaded event model
* Demo: event-loop.js

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* Subscribe and use an event emitter
* Streams
* as event emitters:
* on: data and close
* write
* Files as streams
* Demo fs.createReadStream()

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* Some hard rules:
1. You can't create asynchronicity with just js
1. If your building functionality on top of asynchronous APIs,
then your library must be asynchronous!
1. If a function or method uses asynchronous activity to complete its work,
then that function must have an asynchronous interface (returns a promise)!
* Wrapping with promises
* require('util').promisify for node callbacks
new Promise((resolve, reject) => { /...*/ })
* Demo:
* Evolve CoolStringifier
* "static" methods
* ~~Mocha done~~
* test parameter
* Tests function.length
* if > 0, test is async,
* calling done with any non-null argument is failure (matches node callback signature)
* return a promise!

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* Demo: package.json

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