Ky: Sending form-data

[baranovxyz]

Are there any docs?

szmarczak earned $40.00 by resolving this issue!

• Checkout the Issuehunt explorer to discover more funded issues.
• Need some help from other developers? Add your repositories on Issuehunt to raise funds.

[baranovxyz]

In case anyone has any trouble:

const formData = new FormData();
        formData.append("file", file);
        formData.append("hash", hash);
const headers = {
    /* DO NOT SET THIS, WILL NOT WORK "Content-Type": "multipart/form-data", */
};
ky.post(url, {
    body: formData,
    headers
  });

[szmarczak]

Are there any docs?

Currently no, but I think it would be nice to have things clearified :)

[sindresorhus]

@szmarczak Maybe we should throw an error if someone tries to set the Content-Type header when body is a FormData instance?

[LitoMore]

Maybe we should throw an error if someone tries to set the Content-Type header when body is a FormData instance?

Maybe use warning instead of error will be better?

[sindresorhus]

@LitoMore Why?

[sholladay]

Sending form data in Ky is identical to fetch. That is to say:

• Passing a FormData instance as the body causes the Content-Type header to default to multipart/form-data.
• You can still override the Content-Type header if need be, but I'm not aware of any case where this would be useful when using FormData, since the whole point of FormData is to encode the data in that specific format.
• If you want to send the data in application/x-www-form-urlencoded format, then you will need to either:
  
  
  
  • Encode the data with URLSearchParams instead of using FormData (again the Content-Type will be set automatically), or...
  
  
  • Call form.submit() (i.e. use the DOM instead of Ky or fetch)
  
  

As for whether Ky should throw an error for attempting to override the Content-Type header while using FormData, I'm +0.5 in favor of that since it's probably a mistake. One downside is that FormData would be a new global that some users may need to polyfill even if they aren't using FormData themselves. But at least we can add the polyfill to ky-universal to make it easier.

And to be clear, @baranovxyz your code snippet should work regardless of whether headers is undefined, an empty object, or if you specify 'Content-Type': 'multipart/form-data' explicitly. If it doesn't, then that's a bug, and I don't see what could cause it.

[IssueHuntBot]

@issuehunt has funded $40.00 to this issue.

---

• Submit pull request via IssueHunt to receive this reward.
• Want to contribute? Chip in to this issue via IssueHunt.
• Checkout the IssueHunt Issue Explorer to see more funded issues.
• Need help from developers? Add your repository on IssueHunt to raise funds.

[IssueHuntBot]

@sindresorhus has rewarded $36.00 to @szmarczak. See it on IssueHunt

• :moneybag: Total deposit: $40.00
• :tada: Repository reward(0%): $0.00
• :wrench: Service fee(10%): $4.00