利用类似effect去发送请求

[coolpail]

function lastPromise(promiseFn) {
  let resetReturn;
  return function () {
    let cancel = false;
    if (resetReturn) resetReturn();
    resetReturn = () => cancel = true
    return new Promise((resolve) => {
      promiseFn().then((res) => !cancel && resolve(res))
    })
  }
}

let count = 1
let fn = () => new Promise(rs => setTimeout(() => rs(count++)))

let lastGn = lastPromise(fn)

lastGn().then(console.log)
lastGn().then(console.log)
lastGn().then(console.log)

1. 首先闭包一个resetReturn
2. 每次闭包进一个独立的cancel，