message: feat(nested-scroll): optimise constructor
diff: @@ -59,17 +59,15 @@ export default class NestedScroll {
  static nestedScroll?: NestedScroll
  stores: BScroll[]
  constructor(scroll: BScroll) {
  - const baseCtor = this.constructor as typeof NestedScroll
  + let singleton = NestedScroll.nestedScroll
  - // only need an unique NestedScroll instance
  - let singleton = baseCtor.nestedScroll
  - if (!singleton) {
  - singleton = baseCtor.nestedScroll = this
  + if (!(singleton instanceof NestedScroll)) {
  + singleton = NestedScroll.nestedScroll = this
  singleton.stores = []
  }
  singleton.setup(scroll)
  - this.addHooks(scroll)
  + singleton.addHooks(scroll)
  return singleton
  }
  