feat: support objects with prototypes

[BrianHuf]

Add support for objects with prototypes

[Copilot]

Pull Request Overview

This PR adds support for objects with custom prototypes by updating the isJsonObject function to use a more permissive type check. Previously, the function only accepted plain objects (with Object constructor), but now it accepts any non-null object type, enabling the library to handle class instances and objects with custom prototypes.

• Modified isJsonObject to accept objects with any prototype, not just plain objects
• Added comprehensive test coverage for objects with custom prototypes and nested class instances

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/index.ts	Updated isJsonObject to use generic object type check instead of constructor comparison
src/index.spec.ts	Added test suite demonstrating JSON patch generation for class instances with nested objects

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[marcolink]

Thanks for this @BrianHuf 🙏

So far, this lib doesn't explicitly support any JS classes (Date, Map, Set, RegExp, Array) or custom classes. I want to first support built-ins, before supporting custom classes.

depending on what you want to achieve, you could JSON.parse(JSON.stringify(classInstance)) your input before creating a patch.

[BrianHuf]

No problem. Just sharing some changes we're using in a fork.

For us, it's all about performance. We were using the JSON.parse(JSON.stringify(classInstance)) approach, but profiling showed it being our bottleneck. In our case, classInstance is a proxy (something like https://github.com/immerjs/immer) so stringify is fairy slow.

Another necessary change for performance (for us) is to do object equality checks. For example,

  function compareObjects(path: string, leftJsonValue: any, rightJsonValue: any) {
    if (leftJsonValue === rightJsonValue) {
      return;
    }
   ...

Thanks for the making this library! It's fast, small, and very easy to read.

[marcolink]

Hey @BrianHuf,

Have you explored to only compare the state product of immer instances instead of the full proxy object?

[BrianHuf]

Thanks for the thoughtful suggestion! It's true unwrapping the proxy object would solve the problem.