vyce but with a getter setter api

denam.js

let comps = [],
  isFn = x => typeof x === 'function';

function store(init) {
  let $,
    x = init,
    subs = [];  

  return $ = {
    get value() {
      let comp = comps[comps.length - 1];
      if (comp) $.sub(comp, false);
      return x;
    },
    
    set value(v) {
      x = v;
      for (let sub of subs) sub(x);
    },
    
    sub(fn, run = true) {
      if (run) fn(x);
      if (!~subs.indexOf(fn)) subs.push(fn);
      return idx =>
        (~(idx = subs.indexOf(fn))) && subs.splice(idx, 1);
    },
    
    end: _ => subs = []
  };
}

function computed(fn) {
  let comb = store(),
    calc = _ => {
      if (~comps.indexOf(calc))
        throw Error('Circular Dependency');
      comps.push(calc);
      comb.value = fn();
      comps.pop();
    }
  
  calc();
  return comb;
}

const authors = store([
    { name: 'haruki', age: 25 },
    { name: 'james', age: 32 },
    { name: 'agatha', age: 62 }
]);

const youngAuthors = computed(() =>
    authors.value.filter(author => author.age < 40)
);

console.log(youngAuthors.value);

authors.value = [
  ...authors.value,
  { name: 'david', age: 28 },
  { name: 'lovecraft', age: 57 }
];

console.log(youngAuthors.value);

let comps = [],
  isFn = x => typeof x === 'function';

class Store {
  constructor(init) {
    this._value = init;
    this.subs = [];
  }
  
  get value() {
    let comp = comps[comps.length - 1];
    if (comp) this.sub(comp, false);
    return this._value;
  }
  
  set value(v) {
    this._value = v;
    for (let sub of this.subs) sub(v);
  }
  
  sub(fn, run = true) {
    let subs = this.subs;
    if (run) fn(this._value);
    if (!~subs.indexOf(fn)) subs.push(fn);
    return idx =>
      (~(idx = subs.indexOf(fn))) && subs.splice(idx, 1);
  }
  
  end() {
    this.subs = [];
  }
}

const store = init => new Store(init);

function computed(fn) {
  let comb = store(),
    calc = _ => {
      if (~comps.indexOf(calc))
        throw Error('Circular Dependency');
      comps.push(calc);
      comb.value = fn();
      comps.pop();
    }
  
  calc();
  return comb;
}

const authors = store([
    { name: 'haruki', age: 25 },
    { name: 'james', age: 32 },
    { name: 'agatha', age: 62 }
]);

const youngAuthors = computed(() =>
    authors.value.filter(author => author.age < 40)
);

console.log(youngAuthors.value);

authors.value = [
  ...authors.value,
  { name: 'david', age: 28 },
  { name: 'lovecraft', age: 57 }
];

console.log(youngAuthors.value);