jsketcher/modules/lstream/state.js

import {Emitter} from './emitter';

export class StateStream extends Emitter {

  constructor(initialValue) {
    super();
    this._value = initialValue;
  }
  
  get value() {
    return this._value;
  }

  set value(v) {
    this.next(v);
  }

  next(v) {
    this._value = v;
    super.next(v);
  }

  update(updater) {
    this.value = updater(this._value);
  }

  mutate(mutator) {
    mutator(this._value);
    this.next(this._value);
  }

  attach(observer) {
    observer(this._value);
    return super.attach(observer);
  }
}