javascript - 使动态创建的 promise 按顺序执行

Question

如何动态创建一系列 promise 并让它们按顺序执行？

pseudocode
 for x=0 to maxValue
   promiseArray.push(createNewPromise(x))

 executeAllPromisesSequentially(promiseArray)

在哪里

executeAllPromisesSequentially is functionally equivalent to

promise1()
.then(promise2)
.then(promise3)
etc
...

Answer 1

我的 gist 上显示了一些图案

使用 Reduce 的 Promise 迭代

let tasks = [ /* ... */ ]
let promise = tasks.reduce((prev, task) => {
  return prev.then(() => {
    return task();
  });
}, Promise.resolve());
promise.then(() => {
//All tasks completed
});

顺序迭代模式

let tasks = [ /* ... */ ]
let promise = Promise.resolve();
tasks.forEach(task => {
  promise = promise.then(() => {
    return task();
  });
});
promise.then(() => {
//All tasks completed
});

顺序迭代示例

function spiderLinks(currentUrl, body, nesting) {
  let promise = Promise.resolve();
  if(nesting === 0) {
    return promise;
  }
  const links = utilities.getPageLinks(currentUrl, body);
  links.forEach(link => {
    promise = promise.then(() => spider(link, nesting - 1));
  });
  return promise;
}