node.js - 等待所有流完成 - 流式传输文件目录

Question

我正在使用 client.upload在 pkgcloud上传文件目录。在所有流完成后如何执行回调？是否有内置方法来注册每个流的“完成”事件并在它们全部触发后执行回调？

var filesToUpload = fs.readdirSync("./local_path"); // will make this async

for(let file of filesToUpload) {
    var writeStream = client.upload({
        container: "mycontainer",
        remote: file
    });
    // seems like I should register finish events with something
    writeStream.on("finish", registerThisWithSomething);
    fs.createReadStream("./local_path/" + file).pipe(writeStream);
}

Answer 1

一种方法是生成 Promise每次上传的任务，然后使用 Promise.all() .

假设您使用的是 ES6，那么代码将如下所示:

    const uploadTasks = filesToUpload.map((file) => new Promise((resolve, reject) => {
        var writeStream = client.upload({
            container: "mycontainer",
            remote: file,
        });
        // seems like i should register finish events with something
        writeStream.on("finish", resolve);
        fs.createReadStream("./local_path/" + file).pipe(writeStream);
    });

    Promise.all(uploadTasks)
      .then(() => { console.log('All uploads completed.'); });

或者，如果您有权访问 async / await - 你可以利用它。例如:

    const uploadFile = (file) => new Promise((resolve, reject) => {
      const writeStream = client.upload({
        container: "mycontainer",
        remote: file,
      });
      writeStream.on("finish", resolve);
      fs.createReadStream("./local_path/" + file).pipe(writeStream);
    }
    
    const uploadFiles = async (files) => {
      for(let file of files) {
        await uploadFile(file);
      }
    }

    await uploadFiles(filesToUpload);
    console.log('All uploads completed.');