typescript - while for promise

Question

我有一个大型阵列,它被分成更小的块.然后我对每个块进行异步调用:

  myFunc(arrObjs: any[], chunkSize: number): Promise<any> {
    let result = Promise.resolve(); // To start the chain

    while(arrObjs.length) {
      // Extracting array chunk
      let chunk = arrObjs.splice(0, chunkSize);
      // Building the chain
      result = result.then(() => {
        return someAsynFunc(
          chunk
        );
      });
    }
    return result;
  }

高于我的解决方案 我需要按顺序运行异步函数(系列承诺),所以我构建了一系列promise.

有没有更好的方法来做到这一点？

Answer 1

是的,您可以使用以下reduce模式:

function myFunc(arrObjs: any[], chunkSize: number): Promise<any> {
    const chunks : any[] = [];
    while (arrObjs.length) {
        chunks.push(arrObjs.splice(0, chunkSize));
    }

    return chunks.reduce((p : Promise<any>, chunk : any[]) => {
        return p.then(() => someAsyncFunc(chunk));
    }, Promise.resolve());
  }

(我想我有那些类型的注释是正确的;如果没有,希望你能读过去...)

请注意,我保留了原始行为实际上从arrObjs数组中删除数据,但通常我不主张更改从调用者传递的对象.

这是一个例子:

function myFunc(arrObjs, chunkSize) {
  const chunks = [];
  while (arrObjs.length) {
    chunks.push(arrObjs.splice(0, chunkSize));
  }

  return chunks.reduce((p, chunk) => {
    return p.then(() => someAsyncFunc(chunk));
  }, Promise.resolve());
}

function someAsyncFunc(chunk) {
  console.log("Start handling", JSON.stringify(chunk));
  return new Promise(resolve => {
    setTimeout(() => {
      console.log("Done handling", JSON.stringify(chunk));
      resolve();
    }, 800);
  });
}

const array = [0, 1, 2, 4, 5, 6, 7, 8, 9];
myFunc(array, 3).then(() => {
  console.log("Done");
});

另请注意,上面的内容会在处理之前从阵列中删除所有块.如果你想这样做,因为他们正在处理(与任何产生串扰其他使用该数组,这可能添加/删除/等),你可以做同样的事情,只是没有reduce:

// Cross-talky version
function myFunc(arrObjs : any[], chunkSize : number) : Promise<any> {
  return new Promise<any>(function processChunk(resolve : function) {
    const chunk : any[] = arrObjs.splice(0, chunkSize);
    if (chunk.length == 0) {
      resolve();
    } else {
      someAsyncFunc(chunk).then(() => processChunk(resolve));
    }
  });
}

// Cross-talky version
function myFunc(arrObjs, chunkSize) {
  return new Promise(function processChunk(resolve) {
    const chunk = arrObjs.splice(0, chunkSize);
    if (chunk.length == 0) {
      resolve();
    } else {
      someAsyncFunc(chunk).then(() => processChunk(resolve));
    }
  });
}

function someAsyncFunc(chunk) {
  console.log("Start handling", JSON.stringify(chunk));
  return new Promise(resolve => {
    setTimeout(() => {
      console.log("Done handling", JSON.stringify(chunk));
      resolve();
    }, 800);
  });
}

const array = [0, 1, 2, 4, 5, 6, 7, 8, 9];
myFunc(array, 3).then(() => {
  console.log("Done");
});
setTimeout(() => {
  array.splice(2, 0, 'cross', 'talk');
}, 1000);