Unexpected behavior with plain equality in _where

[Omar-Tnt04]

I was trying to use _where for simple equality filtering and noticed a difference compared to standard query params.

Steps to reproduce

Minimal db.json:

{
  "posts": [
    { "id": "1", "title": "foo" }
  ]
}

Start the server:

npx json-server db.json

Compare these requests:

curl "http://localhost:3000/posts?title=foo"
curl "http://localhost:3000/posts?_where=%7B%22title%22%3A%22foo%22%7D"
curl "http://localhost:3000/posts?_where=%7B%22title%22%3A%7B%22eq%22%3A%22foo%22%7D%7D"

Actual behavior

• title=foo returns the expected post:

[
  {
    "id": "1",
    "title": "foo"
  }
]

• _where={"title":"foo"} returns an empty array:

[]

• _where={"title":{"eq":"foo"}} returns the expected post:

[
  {
    "id": "1",
    "title": "foo"
  }
]

Expected behavior

I initially expected _where={"title":"foo"} to behave like a simple equality filter, similar to title=foo.

If this is not intended, it might be helpful to document that _where requires operator objects, for example:

{ "title": { "eq": "foo" } }

Why this is confusing

For standard query params, title=foo works as an equality filter. Since _where accepts a JSON object, I assumed { "title": "foo" } would be the equivalent form.

The current behavior silently returns no results, so it's not immediately clear whether the query is incorrect or just not matching anything.

Environment

• json-server version: 1.0.0-beta.15
• node version: v24.12.0
• OS: Windows
• Tested with: curl.exe

[Ballursajeed]

Currently _where accepts raw JSON and overrides filters.

However:

• ?title=foo works
• _where={"title":"foo"} returns []

This inconsistency may confuse users.

Proposed options:

1. Normalize primitive values to eq operator
2. Throw validation error
3. Document requirement clearly

Happy to work on a fix.

[Omar-Tnt04]

I agree that the main issue is the inconsistency from the user point of view: ?title=foo works as equality filtering, while _where={"title":"foo"} looks like the same idea but returns an empty array.

I think the safest first step would be to document the requirement clearly, because changing behavior could affect existing users. A note could explain that _where expects operator syntax, for example:

_where={"title":{"eq":"foo"}}

If maintainers prefer a behavior change, then normalizing primitive values to the eq operator would also feel intuitive to users.

I’d be happy to help with a small documentation PR if that direction is welcome.