NodeJS中的异步foreach或for循环

Question

我是NodeJs的初学者，请原谅。下面的lambda函数是在S3中压缩/压缩文件，并将压缩后的文件上传回S3。ListOfKeys包含要压缩的键的列表。如果您注意到（listOfKeys中的const file）的，那么如果有一个大的数据集，即listOfKeys有很长的键列表，则会同步运行得到的lambda超时。问题是，是否有一种方法可以异步或并行地运行循环，以便及时或异步地压缩文件？

代码：

const AWS = require('aws-sdk');
const archiver = require('archiver');
const stream = require('stream');
const request = require('request');

const awsOptions = {
    region: 'us-east-1'
};
const s3 = new AWS.S3(awsOptions);

const streamTo = (bucket, key) =>{};

const getStream = (bucket, key) => {};

exports.handler = async (event, context, callback) => {

    const listOfKeys = [];
    // some code here..
    listOfKeys.push(...contents.map(x => x.Key));

    await new Promise(async (resolve, reject) => {
        var zipStream = streamTo(SrcBucket, destinationKey);
        zipStream.on("close", resolve);
        zipStream.on("end", resolve);
        zipStream.on("error", reject);
        var archive = archiver("zip");
        archive.on("error", err => {
            throw new Error(err);
        });
        archive.pipe(zipStream);

        for (const file in listOfKeys) {
            archive.append(getStream(SrcBucket, listOfKeys[file]), { name: listOfKeys[file].split('/')[3] });
        }

        archive.finalize();
    }).catch(err => {
        throw new Error(err);
    });

    callback(null, {
        body: { final_destination: destinationKey }
    });
};




Answer 1

我可能会更加灵活地重写整个内容，但为了回答您的具体问题：将ListOfKeys.foreach语句替换为：

await Promise
  .all(
    listOfKeys.map(key => archive.append(getStream(SrcBucket, key), { name: key.split('/')[3] }))
  );

Answer 2

const array1 = ['a', 'b', 'c'];

array1.forEach(element => console.log(element));

// expected output: "a"
// expected output: "b"
// expected output: "c"

所以您的代码应该是：

listOfKeys.forEach(file => {
    archive.append(getStream(SrcBucket, listOfKeys[file]), { name: listOfKeys[file].split('/')[3] })
})

（不确定是否可行，请告诉我）

源：array.prototype.foreach（）MDN