Best way to handle forms that collect parent and nested record data?

[KieranP]

Simple example: Post has many metadata. Create a form that takes post data, and under metadata section, you can add multiple metadata records.

In Rails, I would use the convention of square brackets. e.g. post[name], post[metadata][][name] (or post[metadata][0][name]). And the resulting params when submitted would be parsed as:

{
  post: {
    name: '...',
    metadata: [
      {
        name: '...',
      }
    ]
  }
}

In SvelteKit however there appears to be no built in way to handle this? The request.formData() returns a simple JS map, with keys and values, nothing nested, which makes sense, because this isn't an HTTP standard.

I am wondering however, what is the best way to handle this? Are their popular libraries that handle this? Or is it just a case of rolling my own function?

[brunnerh]

The object returned is a FormData instance, which has limited support for creating arrays by adding multiple values for the same key, which then can be retrieved via getAll.

If you really need deeper nesting, you could look for a library (there is e.g. qs, but it has an unnecessarily high number of dependencies).

In case your page requires JS to function properly, you could also send a nested object directly as JSON and parse that on the server. This is generally not recommended; forms should ideally still work in cases where the JS failed to load which can e.g. happen with unstable network conditions.