Question

我需要使用延迟调用外部服务器来处理对象数组，将所有结果收集到数组中并进行后处理。示例在这里：

(async () => {
  const serverOperation = () => new Promise(resolve => setTimeout(() => resolve(), 2000));
  const myOtherFunction = results => console.log('results', results);
  const objectsArray = [{}, {}, {}];
  const results = [];

  const myFunc = async arr => {
    const el = arr.shift();

    if (!el) {
      // finish of calling recursive function
      return;
    }

    // some big server operation
    const result = await serverOperation();

    results.push(result);

    // need to wait for some time
    setTimeout(async () => {
      console.log(Date.now());
      await myFunc(arr);
    }, 3000);
  };

  await myFunc(objectsArray);
  await myOtherFunction(results);  // <= postprocessing results
})();

问题是：在获得所有结果之前，函数myOtherFunction已被调用。

我的问题是：如何对所有处理后的结果进行后处理？

Answer 1

您可以使用超时承诺而不是setTimeout来延迟函数的执行。

代码的问题在于，即使将async函数传递给setTimeout，它也不会停止当前函数的执行。 setTimeout只会将任务移至微任务队列并执行传递给它的函数。但这不会导致父函数停止，因为传递给setTimeout的函数不会立即调用-稍后会在不同的时间，不同的位置调用它。

(async () => {
  const serverOperation = () => new Promise(resolve => setTimeout(() => resolve('server op'), 2000));
  const myOtherFunction = results => console.log('results', results);
  const objectsArray = [{}, {}, {}];
  const results = [];
  
  // used for delaying operations
  const timeoutPromise = () => new Promise(resolve => setTimeout(() => resolve(), 3000));

  const myFunc = async arr => {
    const el = arr.shift();

    if (!el) {
      // finish of calling recursive function
      return;
    }

    // some big server operation
    const result = await serverOperation();

    results.push(result);

    // need to wait for some time
    await timeoutPromise();
    
    console.log(Date.now());
    
    await myFunc(arr);
  };

  await myFunc(objectsArray);
  await myOtherFunction(results);  // <= postprocessing results
})();

Node.js：调用递归函数的后处理结果

1 个答案: