Base Mdoel es6

base.es6

function belongsto(Class, property, descriptor) {
  return {
    get() {
      return descriptor.get().find(this[property+'Id'])
    },
    set(id) {
      return this[property+'Id'] = id.id || id
    }
  }
}
function hasOne(Class, property, descriptor) {
  return {
    get() {
      var cache = descriptor.get().cache
      for(var key in cache) {
        if(cache[key][property+'Id'] === this.id) {
          return cache[key]
        }
      }
    },
    set(id) {
      descriptor.get().find(id)[property+'Id'] = this.id
    }
  }
}

function hasMany(Class, property, descriptor) {
  property = property.replace(/s$/, '')
  return {
    get() {
      var cache = descriptor.get().cache
      var result = []
      for(var key in cache) {
        if(cache[key][property+'Id'] === this.id) {
          result.push(cache[key])
        }
      }
      return result
    },
    set(ids) {
      ids.map(id => descriptor.get().find(id)[property+'Id']=this.id)
    }
  }
}


const CACHE = Symbol('cache')

class Model {
  static get cache() {
    return this[CACHE] || (this[CACHE]={})
  }
  static find(id) {
    return this.cache[id]
  }
  @belongsto
  get model() {
    return Model
  }
  @hasMany
  get models() {
    return Model
  }
  constructor(data) {
    Object.assign(this, data)
    this.constructor.cache[this.id] = this
  }
}


var model = new Model({id: 5})
var m = new Model({model: model})