text: import { each } from './tools'
  var _Observable = function () {
    this.observers = []
  }
  _Observable.prototype = {
    subscribe: function (f) {
      this.observers.push(f)
    },
    notify: function (data) {
      each(this.observers, function (observer) {
        observer(data)
      })
    }
  }
  export var Observable = _Observable
  