Very simple dependency tracker system like in vue.js

dep.js

function Dependency(name, value, cb = null) {
	this.name = name
  this.value = value
	this.callback = cb  
}

function DependencyTracker() {
  this._stack = [];
  
  this.add = function(dep) {
    this._stack.push(dep);
    return () => this.remove(dep)
  }
  
  this.remove = function(dep) {
    this._stack = this._stack.filter((d) => d != dep)
  }
  
  this.notify = function(dep) {
   	this._stack
    	.filter((d) => d.name == dep.name)
      .forEach((d) => d.callback())
  }
}

const tracker = new DependencyTracker();

function createWatcher(name, value) {
  const context = {
  	name,
   	value,
  } 
  
  let _dep
  
  function fn(cb){
    _dep = new Dependency(name, value, cb)
    return tracker.add(_dep)
  }
  
  Object.defineProperty((window || global || this_), context.name, {
  	get() {
    	return context.value;
    },
    set(value) {
      context.value = value;
      tracker.notify(_dep);
    }
  });
  
  return fn
}

const watch = createWatcher('x', 10)

const unwatch = watch(function() {
  console.log('watcher')
})

const unwatch2 = watch(function() {
  console.log('watcher 2')
})