RINSE

REPEAT

The Node.js event loop and how it works.

Vitor Fernandes

https://github.com/vmlf01/nodejs-rinse-repeat

TopTal Developer @ KWAN

github.com/vmlf01

http://merge.kwan.pt/

Summary

• the motive behind node.js

• node architecture

• the event loop

The Motive

Behind
Node.js

Created 2009 by Ryan Dahl

why?

because I/O is slow

http://www.eecs.berkeley.edu/~rcs/research/interactive_latency.html

Latency numbers every programmer should know

so the idea is:

I/O needs to be done differently

node.js uses an

instead of blocking

event loop

on the cpu

for events

Node

Architecture

The

Event

Loop

Philip Roberts: What the heck is the event loop anyway?

must see

let's try out the demo!

Call Stack

callback queue

the human node simulator

callback queue

event loop

v8 engine

worker thread

client app

client app

worker thread

client app

The V8 engine has a

Call Stack

and a

Heap*

* it's got memory

everything else

is provided by the host,

be it the

browser

or

Node.js

so

Node.js

is essentialy a

runtime environment

CODE

SAMPLES

create an index.js file with:

console.log('Hello World');

and run it with:

$ node index.js

node will execute the script

inside index.js and exit

that's because

there was nothing else to do!

change index.js to:

setTimeout(function () {
    console.log('Hello World');
}, 5000);

and run it again:

$ node index.js

now the application will only

terminate after the

setTimeout

callback is executed

don't block,

collaborate

you have a lot of nanoseconds

at your disposal

thank you!

RINSE

REPEAT