在 promise 内的 setTimeout 之后解析 promise

Question

I would like to resolve my promise after my setTimeout will be finished. I have a few functions like step The main idea is to get step results sequentially. PS we can't mutate setTimeout.

function step (done) {
  return new Promise((resolve, reject) => {
    try {
      setTimeout(done, 5100, 'hello world')
      resolve()
    } catch (error) {
      reject()
    }
  })
}

Answer 1

If you can't mutate the setTimeout remove it. Instead of putting the setTimeout in the step function create a new delay function that returns a promise. You can then use async/await to walk through the steps after certain delays.

 function delay(time = 1000) { return new Promise(res => { setTimeout(() => res(), time); }); } function step(fn, n) { fn(`hello world ${n}`); } const fn = (str) => console.log(str); async function main() { step(fn, 1); await delay(5000); step(fn, 2); await delay(3000); step(fn, 3); } main();

Answer 2

If you can change the done function, you can do like below.

 function step(done) { return new Promise((resolve, reject) => { immutableFunc(done(resolve, reject)); }); } function immutableFunc(done) { setTimeout(done, 1000, "hello world"); } function done(resolve, reject) { return arg => { try { console.log(arg); resolve(); } catch (error) { reject(error); } }; } async function test() { try { await step(done); await step(done); await step(done); } catch (err) { console.log(err); } } test();