Typescript async await not working

Question

I have the following async function in Typescript, and it seems that await doesn't block and yield the required result as I expect.

async function getCroppedImgContent(origImgBuffer: Buffer) {
  console.log("Inside setCroppedImgContent");
  let croppedBuffer =  await sharp(origImgBuffer)
    .resize(4000, 4000)
    .max()
    .toBuffer();
  console.log("After crop");

  return croppedBuffer;
}

"After crop" is not print immediately after "Inside setCroppedImgContent", but a lot later. Looks like await is not working.

Does sharp().resize().max().toBuffer() return a promise because await is only really useful when you are awaiting a promise. — jfriend00
– jfriend00, Commented Aug 12, 2017 at 17:43
The execution is not blocked at the await line, result is returned later — Nenad
– Nenad, Commented Aug 12, 2017 at 17:44
@jfriend00 yes, it does: https://github.com/lovell/sharp#examples — alexmac
– alexmac, Commented Aug 12, 2017 at 17:45

Thiago Barcala · Accepted Answer · 2017-08-12 18:40:47Z

2

Nenad, the fact that you used await inside your function does not mean it will be executed synchronously. await just makes the execution be blocked for a single call.

If you want console.log("After setCroppedImgContent"); to be executed after getCroppedImgContent is completed you need to await its call:

await getCroppedImgContent(origContent)
    .then(function (croppedBuffer) {
    image.content = croppedBuffer;
    console.log("Set image content");
});

edited Aug 12, 2017 at 18:40

answered Aug 12, 2017 at 18:28

Thiago Barcala

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4 Comments

alexmac Over a year ago

But in this case this code should be added to a new function, and marked with async keyword.

Nenad Over a year ago

What about "After crop", shouldn't it be printed after "Inside setCroppedImgContent" ? In my case it isn't, and that's my biggest problem. I have added the calling code because of the comments, but it's irrelevant.

Thiago Barcala Over a year ago

Now you changed your description completely, and it seems what I would consider correct behaviour.

Thiago Barcala Over a year ago

"After crop" is not printed immediately because the execution is blocked waiting for the Promise to be completed.

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