Meta js

Welcome to my rant

Before diving into deep thoughts

Warnings

Purely experimental

Diabolical in nature

No "Public" documentation

Don't use in production

I repeat, don't use in production

About

Generators

Coroutines

may be Proxy

may be Symbols

Types of functions

Generators

function* willItRunForever() {
  let count = 0;
  while(true) {
    yield;
    console.log(count);
    count++
  }
}

Hello World

function* Hello() {	
  yield 1;
  
  console.log('exiting');
}

How do i call this?

It's not your normal function.

Call to `hello()` returns object. YES object!!!

WHAT the function?

Well,

function* Hello() {	
  yield 1;
  console.log('exiting');
}

// gen is a object, object, object
const gen = Hello();
// to acutally make run the 
// function upto the first `yield`.
// returns object { value : 1, done: false}
// `done: false`  means function is not done
const result = gen.next();
// to run the rest of the statements in function
gen.next();
// done

function* MoreHello() {	
  yield 1;
  yield 2;
  console.log("done");
}

// YUP
const gen = MoreHello();
// upto first yield
const result = gen.next(); 
console.log(result.value, result.done) // ??
// upto second yield
const again = gen.next();
console.log(result.value, result.done) // ??
// upto `return`
const last = gen.next();
console.log(result.value, result.done) // ??
// done

LEVEL 1

function* forever() {	
  let count = 0;
  while(true) {
    yield count;
    count++
  }
}

Infinite Counter

LEVEL Fibonacci

function* fib() {
  let a = 0,
      b = 1;
  while(true) {
    yield a;
    temp = a;
    a = b;
    b = temp + b;
  }
}

Any THOUGHTS ?

function* foo() {
  console.log("FIRST call");
  yield 1;
  console.log("SECOND call");
  yield 2;
  console.log('PLEASE STOP');
}

Caller takes a control 
back

Thoughts?

Why control is given back to caller

Why can't my function execute without being paused and just freaking run until function ends?

everytime it hits `yeild`?

Why would anyone think 
of such function that pause?

I don't use but who the f uses it ?

DEEP Thoughts?

Where am i going?

Turns out your event loop uses it all the time

But HOW?

Imagine Me

as a event loop

and watch deeply

DEMO TIME......

TASK 1: Even Counter

TASK 2: Odd Counter

Event loop

Output

Even Task runs and

Odd Task runs and

Even Task runs and

Odd Task runs and

Even Task runs and

Odd Task runs and

Even Task runs and

Odd Task runs and

Even Task runs and

Control is back to caller(event loop).

Odd Task runs and

Control is back to caller(event loop).

AGAIN

Even Task runs and

.........

yield

REAL LIFE

TASK 1

TASK 2

Tasks run one after another.

It's Asynchronous.

It's Concurrent.

But not parallel

TAKE AWAY

JS deals multiple things at the same time but does not run multiple things at the same time.

Concurrent but not parallel.

OKAY

That's cute.

Async/Await uses generators.

Is there is any other uses of generators?

WELL

As a Context manager

As a State Machine

Notice Something?

As a Iterator

As a Tree/Graph traversal

Notice Something?

As a zero memory allocated data transormer

Basically, 
Sky is the limit

THESE DAYS

DEEP DIABOLICAL EXPERIMENT WITH COROUTINES

building GC friendly parallel stream processing compute pipeline

Quick tour (SMALL SCALE)

Number Parser NODE

Odd filter NODE

Odd filter NODE

Prime filter NODE

Source

Number
Parser

Odd
Filter

Prime
Filter

Sink

OR?

FILE

Number parser

Even

Odd

Prime

<100

>100

Socket

Console

FANOUT?

OR?

Parallalized??

USING DIFFERENT EXECUTOR ENGINE