AsyncTaskQueue.js

class TaskList {
  constructor(tasks) {
    this.tasks = tasks
    this.promise = null
    this.index = 0
    this.fowarding = false
  }

  async start() {
    this.fowarding = true
    let promise = this.promise = Promise.resolve()
    this.tasks.forEach((task) => {
      promise = promise.then((...args) => {
        this.index++
        if (this.forwarding = false) {
          return args
        } else {
          return task.forward(...args)
        }
      })
    })
    return promise
  }

  cancel() {
    this.fowarding = false
    let promise = this.promise
    this.tasks.slice(0, this.index).forEach((task) => {
      if (!task.needCancel) {
        return
      }
      promise = promise.then((...args) => {
        return task.backward(...args)
      })
    })
    return promise
  }
}

let a = 1, b = 2
const tl = new TaskList([
  {
    forward: async () => {
      a = 2
      return new Promise((res) => {
        setTimeout(() => {
          res('finish')
        }, 10000)
      })
    },
    backward: async () => {
      a = 1
    },
    needCancel: true,
  },
  {
    forward: async () => {
      b = 8
    },
    backward: async () => {
      b = 2
    },
    needCancel: false,
  },
])

tl.start().then(() => {
  console.log('in start', a, b)
})
setTimeout(() => {
  console.log('waiting', a, b)
}, 200)
setTimeout(() => {
  tl.cancel().then(() => {
    console.log('in cancel', a, b)
  })
}, 1000)