Function track

packages/reactivity/src/dep.ts:262–284

(target: object, type: TrackOpTypes, key: unknown)

 * @param key - Identifier of the reactive property to track.
 */
export function track(target: object, type: TrackOpTypes, key: unknown): void {
  if (shouldTrack && activeSub) {
    let depsMap = targetMap.get(target)
    if (!depsMap) {
      targetMap.set(target, (depsMap = new Map()))
    }
    let dep = depsMap.get(key)
    if (!dep) {
      depsMap.set(key, (dep = new Dep()))
      dep.map = depsMap
      dep.key = key
    }
    if (__DEV__) {
      dep.track({
        target,
        type,
        key,
      })
    } else {
      dep.track()
    }
  }
}

/**
 * Finds all deps associated with the target (or a specific property) and