我如何按顺序执行异步代码？

Question

    await fs.mkdir(path.join(__dirname, "/smartsheet_download"), 
   { recursive: true }, (err) => { 
     if (err) { 
       return console.error(err); 
     } 
     __dirname= path.join(__dirname, "/smartsheet_download");
   console.log("after func:" + __dirname);
   })

   console.log("this must be printed after path at last")
}

my question in this above function is i am printing "this must be printed after path at last" after the fs.mkdir operation but when i am running the code it prints first. i am using async and await so that it must wait for fs.mkdir to complete the execution before printing the last line. Still this thing does not work. Could u please tell how can i wait for fs.mkdir to complete and then pass the execution to next line. moreover, please tell why await do not work here?

Answer 1

your logic is correct. however, if you look at the signature of fs.mikdir it returns void

export function mkdir(path: PathLike, options: MakeDirectoryOptions & { recursive: true }, callback: (err: NodeJS.ErrnoException | null, path: string) => void): void; <---

which means, it cannot be await ed, although it executes an async task, but due it returns void, it cannot be awaited.

the callback exists for when you need to know if the what happend to the operation, succesed/faild something like that, thats why your log happens before, because mkdir returns void.

so if you need do something after fs.mikdir was finished. you can use fs.mkdirSync which will block execution of code untill the call has finsished, or just do your work in the callback you pass to the function

fs.mkdir(path.join(__dirname, "/smartsheet_download"), 
   { recursive: true }, (err) => { 
     if (err) { 
       return console.error(err); 
     } 
     __dirname= path.join(__dirname, "/smartsheet_download");
   console.log("after func:" + __dirname);

 console.log("this must be printed after path at last")
   })