c.json returning empty string for undefined values

[marcosrjjunior]

I'm mainly creating this ticket to understand a bit more about why this is happening and potentially flag an issue.

One of my functions was returning undefined instead of false and the c.json is forcing the response to be an "" (empty string) instead of throwing an error.

Response: ""

---

Reading the json implementation here (hopefully that is the correct place).

I noticed that there possibly some extra things going on there:

• JSON.stringify(object). Why do we need to run throguh a JSON.stringify before returning?
• Re-creating the response

Because of the issues mentioned above I replaced it to use the main response instead.

[yusukebe]

Hi @marcosrjjunior !

Thanks for your comment. I think we can follow the Response.json() spec, but the results/content of Response.json(undefined) seem to be different between runtimes. Which runtime do you run it on?

By investigating, results are below:

• Cloudflare Workers - "undefined"
• Bun - ""
• Deno - throw an error
• Node.js - throw an error

Ideally, undefined can't be serialized in JSON, so I think it should thows an error.

[yusukebe]

Indeed, according to MDN, it should throw an error if it's undefined.

https://developer.mozilla.org/en-US/docs/Web/API/Response/json_static#typeerror

[marcosrjjunior]

hey @yusukebe thanks for the quick reply.

I'm getting "" empty strings for both Nodejs and Bun, that is the issue.

I agree, it should thrown an error instead.

// ...
"hono": "^4.0.10",

"@hono/node-server": "^1.8.2",

[yusukebe]

@marcosrjjunior

Thanks. I think the better way is to use Response.json() inside c.json(). When Hono was first developed, Response.json() was not implemented in all runtimes, so it is not used.

[marcosrjjunior]

that would be great @yusukebe!
leaving the c.json as close the the Response.json as possible without any other extra logic.