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Hayden Library - RM666.C266 N49 2019

Hayden Library - RM666.C266 F79 2018

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Estigmatizados como focos de contagio en algunos países, los trabajadores de la salud han sido agredidos, maltratados y marginados.

Fighting between the Indian Army and militants threatened to heighten hostilities in the disputed region, where near-daily skirmishes have raged for weeks.

Over years of fighting, Riyaz Ahmad Naikoo recruited scores of young Kashmiris in an armed quest for independence from India. His death has set off a fresh wave of unrest.

In this post I will talk about Events and Promise limits, trying to fill all gaps with a 498 bytes sized library called notify-js.

Update
The awesome Lie function got improved and became an official module (yet 30 lines of code thought). Its name is Dodgy, and it's tested and even more awesome!

Not today though, today is just fine

1. if we are in charge of creating the Promise, we are the only one that could possibly make it abortable and only if we want to, it's an opt in rather than a default or a "boring to write" subclass
2. it's widely agreed that cancellation should be rather synonymous of a rejection, there's no forever pending issue there, just a plain simple rejection
3. one of the Promise strength is its private scope callback, which is inevitably the only place where defining abortability would make sense. Take a request, a timer, an event handler defined inside that callback, where else would you provide the ability to explicitly abort and cleanup the behavior if not there?
4. being the callback the best pace to resolve, reject, and optionally to abort, that's also the very same place we want to be sure that if there was a reason to abort we can pass it along the rejection, so that we could simply ignore it in our optionally abort aware Promises, and yet drop out from any other in the chain whenever the rejection occurs or it's simply ignored
5. the moment we make the promise malleable from the outer world through a p.abort() ability, is also the very same moment we could just decide to resolve, or fully fail the promise via p.resolve(value) or p.reject(error)

var p = new Lie(function (resolve, reject, onAbort) {
  var timeout = setTimeout(resolve, 1000, 'OK');
  // invoking onAbort will explicit our intent to opt-in
  onAbort(function () {
    clearTimeout(timeout);
    return 'aborted'; // will be used as rejected error
                      // it could even be undefined
                      // so it's easier to distinguish
                      // between real errors and aborts
  });
});

p.then(
  console.log.bind(console),
  console.warn.bind(console)
).catch(
  console.error.bind(console)
);

var toTheOuterWorld = p.then(
  function (data) {return data},
  function (error) {return error}
);
// or even ...
var toTheOuterWorld = Promise.resolve(p);

// abortable promise
var cancelable = new Lie(function (r, e, a) {
  var t = setTimeout(r, 5000, 'all good');
  a(function () { clearTimeout(t); });
});

// testing purpose, will it resolve or not?
setTimeout(cancelable.reject, 1000, 'nope');
// and what if we abort before?
setTimeout(cancelable.abort, 750);



// generic promise, let's log what happens
var derived = cancelable.then(
  function (result) { console.log('resolved', result); },
  function (error)  { error ?
    console.warn('rejected', error) :
    console.log('ignoring the .abort() call');
  }
).catch(
  function (error)  { console.error('cought', error); }
);

// being just a Promise, no method will be exposed
console.log(
  derived.resolve,
  derived.reject,
  derived.abort
);

Lie.more = function more(lie) {
  function wrap(previous) {
    return function () {
      var l = previous.apply(lie, arguments);
      l.resolve = lie.resolve;  // optional bonus
      l.reject = lie.reject;    // optional bonus
      l.abort = lie.abort;
      return Lie.more(l);
    };
  }
  if (lie.abort) {
    lie.then = wrap(lie.then);
    lie.catch = wrap(lie.catch);
  }
  return lie;
};

var chainedLie = new Lie(function (res, rej, onAbort) {
  var t = setTimeout(res, 1000, 'OK');
  onAbort(function (why) {
    clearTimeout(t);
    return why;
  });
})
.then(
  console.log.bind(console),
  console.warn.bind(console)
)
.catch(
  console.error.bind(console)
);

// check this out
chainedLie.abort('because');

var justPromise = Promise.resolve(chainedLie);

I love hacks and unusual patterns! As logical consequence, I loved this post about "Real" Mixins!!!
The only hitch about that post is that I believe there are few points closer to a "gonna sell you my idea" discussion than a non disillusioned one.
Let's start this counter analysis remembering what are actually classes in latest JavaScript standard, so that we can move on explaining what's missing in there.

JavaScript embraces prototypal inheritance

// class in ES2015
class A {
  constructor() {}
  method() {}
  get accessor() {}
  set accessor(value) {}
}

// where are those methods and properties defined?
console.log(
  Object.getOwnPropertyNames(A.prototype)
  // ["constructor", "method", "accessor"]
);

function A() {}
Object.defineProperties(
  A.prototype,
  {
    // constructor is implicitly defined
    method: {
      configurable: true,
      writable: true,
      value: function method() {}
    },
    accessor: {
      configurable: true,
      get: function get() {},
      set: function set(value) {}
    }
  }
);

var A = (function () {
  // the constructor
  function A() {
    _classCallCheck(this, _temporalAssertDefined(A, "A", _temporalUndefined) && A);
  }
  // the enriched prototype
  _createClass(_temporalAssertDefined(A, "A", _temporalUndefined) && A, [{
    key: "method",
    value: function method() {}
  }, {
    key: "accessor",
    get: function get() {},
    set: function set(value) {}
  }]);

  return _temporalAssertDefined(A, "A", _temporalUndefined) && A;
})();

The super case

// used within the constructor
let super = (...args) => A.apply(this, arguments);

// used within any other method
super.method = (...args) => A.prototype.method.apply(this, args);

// used as accessor
Object.defineProperty(super, 'accessor', {
  get: () => Object.getOwnPropertyDescriptor(
    A.prototype, 'accessor'
  ).get.call(this),
  set: (value) => Object.getOwnPropertyDescriptor(
    A.prototype, 'accessor'
  ).set.call(this, value)
});

Prototypes are always modified anyway!

When using mixin libraries against prototype objects, the prototypes are directly mutated. This is a problem if the prototype is used anywhere else that the mixed-in properties are not wanted.

super actually should NOT work!

The real, and only, difference between a mixin and normal subclass is that a normal subclass has a fixed superclass, while a mixin definition doesn't yet have a superclass.

• With JavaScript finally supporting super, so should mixins
• super.foo property access works within mixins and subclasses.
• super() calls work in constructors.
• One of the biggest benefits is that super works inside methods of the subclass and the mixins.

super calls can be a little unintuitive for those new to mixins because the superclass isn't known at mixin definition, and sometimes developers expect super to point to the declared superclass (the parameter to the mixin), not the mixin application.

Constructors are a potential source of confusion with mixins. They essentially behave like methods, except that overriden methods tend to have the same signature, while constructors in a inheritance hierarchy often have different signatures.

• any particular extent of space or surface
• a geographical region
• any section reserved for a specific function
• extent, range, or scope
• field of study, or a branch of a field of study
• a piece of unoccupied ground; an open space
• the space or site on which a building stands

Oversold super ability

instanceof what?

// a new anonymous class is created each time
// who's gonna benefit about the instanceof?
let MyMixin = (superclass) => class extends superclass {  
  foo() {
    console.log('foo from MyMixin');
  }
};

// let's try this class
class MyClass extends MyMixin(MyBaseClass) {  
  /* ... */
}

// Justin says it's cool that instanceof works ...
(new MyClass) instanceof MyMixin; // false
// false ... really, it can't be an instance of
// an arrow function prototype, isn't it?!

Improving **Objects** Composition

let mix = (superclass) => new MixinBuilder(superclass);

class MixinBuilder {  
  constructor(superclass) {
    this.superclass = superclass;
  }

  with(...mixins) { 
    return mixins.reduce((c, mixin) => mixin(c), this.superclass);
  }
}

let mix = (object) => ({
  with: (...mixins) => mixins.reduce(
    (c, mixin) => Object.create(
      c, Object.getOwnPropertyDescriptors(mixin)
    ), object)
});

let a = {a: 'a'};
let b = {b: 'b'};
let c = {c: 'c'};
let d = mix(c).with(a, b);
console.log(d);

As Summary ...

1. Mixins are added to the prototype chain.
2. Mixins are applied without modifying existing objects.
3. Mixins do no magic, and don't define new semantics on top of the core language.
4. super.foo property access won't hopefully work within mixins but it will with subclasses methods.
5. super() calls won't hopefully work in mixins constructors because you've no idea what kind of arguments you are going to receive. Subclasses still work as expected.
6. Mixins are able to extend other mixins.
7. instanceof has no reason to be even considered in this scenario since we are composing objects.
8. Mixin definitions do not require library support - they can be written in a universal style and be compatible with non classes based engines too.
9. bonus: less memory consumption overall, there's no runtime duplication for the same logic each time

Hayden Library - GA693.7.A1 A77 2016

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Dewey Library - G1362.C6A5 H46 2017

Dewey Library - GA873.7.A1 M56 2017

Rotch Library - G70.212.Y36 2017

Hayden Library - G151.D47 2017

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Hayden Library - G860.E97 2018

Hayden Library - G151.S57 2018

Rotch Library - G70.212.G489 2018

Rotch Library - G70.212.H358 2017

Rotch Library - G70.212.B35 2018

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