code: function flushWatcherQueue () {
    flushing = true
    let watcher
    let id
  
    queue.sort((a, b) => a.id - b.id)
  
    for (index = 0; index < queue.length; index++) {
      watcher = queue[index]
      id = watcher.id
      has[id] = null
      watcher.run()
      // in dev build, check and stop circular updates.
      if (process.env.NODE_ENV !== 'production') {
        circular[id] = (circular[id] || 0) + 1
        if (circular[id] > MAX_UPDATE_COUNT) {
          console.error(
            `[MIP warn]:You may have an infinite update loop in watcher with expression "${watcher.exp}"`
          )
          break
        }
      }
    }
  
    resetState()
  }
docs: Flush queues and run the watchers.