Javascript 为 Promise.all 中的每个已解析的 Promise 执行一个函数

如果所有promise 都实现，则Promise.all返回一个promise ，该promise 使用一组值进行解析--原始promise 的解析值.因此，您只需迭代该数组并对其执行额外的逻辑.

就像这样:

function fetchData(url) {
  return fetch(url);
}

const urls = [
  'https://api.example.com/data1',
  'https://api.example.com/data2',
  'https://api.example.com/data3'
];

const promises = urls.map(fetchData);
Promise.all(promises).then(arr => {
    arr.forEach(callbackResolve);
});

为了监控进度，您可以对最初的promise 使用单独的.then()个呼叫.例如，按如下方式完成上面的代码:

function fetchData(url) {
  return fetch(url);
}

const urls = [
  'https://api.example.com/data1',
  'https://api.example.com/data2',
  'https://api.example.com/data3'
];

const promises = urls.map(fetchData);

let resolveProgress = 0;
for (const promise of promises) {
    promise.then(() => {
        resolveProgres++;
        console.log("Progress:", 
                    ((resolveProgress / promises.length) * 100).toFixed(2) + "%"
                   );
    });
}

Promise.all(promises).then(arr => {
    arr.forEach(callbackResolve);
});