Typescript Definitions Not Working Properly (Tested on TS 5.9.3)

[lbineau]

Hi! First of all, thank you for this library — it’s looks very helpful and lightweight, and I appreciate the work that has gone into it 🙏
I usually don't do the "hey, it doesn't with TS" guy, since it is stated in the library 📝 Type Safe - Full TypeScript support with comprehensive type definitions, I'd expect the code samples to work with it out of the box.

While trying it with a fresh Vite install with TypeScript 5.9.3, I encountered several issues with the .d.ts definitions that prevent correct type checking. Below are a few examples when I'm using the demo example:

---

1. Property 'success' does not exist on type 'Object'.

// Error:
// Property 'success' does not exist on type 'Object'.ts-plugin(2339)

---

2. Incorrect method signature for RuleHelpers.gte()

// Error:
// Expected at least 3 arguments, but got 2.ts-plugin(2555)
// RuleHelpers.d.ts(47, 32): An argument for 'options' was not provided.

---

3. rules.validation possibly undefined

// Error:
// 'rules.validation' is possibly 'undefined'.ts-plugin(18048)

---

Summary

The TypeScript definitions may need updates to reflect the actual structure and usage patterns of the library.
Thanks again for maintaining this project!

Best regards.

[crafts69guy]

Hi @lbineau! 👋

Thank you for taking the time to report this and for the kind words about the
library! You're absolutely right — the TypeScript definitions were not aligned w
ith the actual implementation, which was a significant oversight on our part.

I'm happy to let you know that all the issues you mentioned have been fixed
in v1.0.4 (current version is v1.0.6):

✅ Fixed Issues:

1. Property 'success' does not exist on type 'Object'

   • evaluateExpr() now explicitly returns EvaluationResult type, so result.success works correctly.

2. Expected at least 3 arguments, but got 2 for RuleHelpers.gte()

   • All comparison methods (gte, eq, lt, etc.) now correctly treat options as optional.

3. 'rules.validation' is possibly 'undefined'

   • Validation helpers are now strictly defined (no longer "possibly undefined").

Additional Fixes:

• PathResolver.resolvePath renamed to resolve to match implementation
• Added missing flags property to StringOptions for regex operator
• Removed unsupported options (caseInsensitive, trim) from types to align
  with actual implementation
• Updated in, notIn, oneOf type definitions to support dynamic array paths

Please update to the latest version:

npm update rule-engine-js

Let me know if you encounter any other TypeScript issues — your feedback is incredibly valuable for improving the library! 🙏

[hyusetiawan]

can you give an example how to type it? is it through generics? Not one example shows how the typing is done, I would assume there is a typeof somewhere when we create the rules or something

[crafts69guy]

can you give an example how to type it? is it through generics? Not one example shows how the typing is done, I would assume there is a typeof somewhere when we create the rules or something

Hi @hyusetiawan! Great question. Here are some practical TypeScript examples:

Basic Usage with Types

import {
 createRuleEngine,
 createRuleHelpers,
 RuleExpression,
 EvaluationContext,
 EvaluationResult
} from 'rule-engine-js';

// Create engine and helpers
const engine = createRuleEngine();
const helpers = createRuleHelpers();

// Define typed context
interface UserContext extends EvaluationContext {
 user: {
  age: number;
  role: string;
  email: string;
 };
}

// Build rules using helpers (fully typed)
const rule: RuleExpression = helpers.and(
 helpers.gte('user.age', 18),
 helpers.eq('user.role', 'admin')
);

// Evaluate with typed context
const context: UserContext = {
 user: { age: 25, role: 'admin', email: 'admin@example.com' }
};

const result: EvaluationResult = engine.evaluateExpr(rule, context);

if (result.success) {
 console.log('User is adult admin');
}

The library doesn't use generics for rule expressions (since rules are JSON-based), but all inputs/outputs have proper type definitions. Let me know if you'd like more examples!

[hyusetiawan]

i think that just types the api, like gte, gt etc but not the data itself, I suggest you use generics. I created a full fledged typing so that even the dot path of the data itself can be detected:
https://gist.github.com/hyusetiawan/0f79794086cb12baf101323e3b44ca8d

you can use this library too: https://github.com/g-makarov/dot-path-value

[crafts69guy]

Hi @hyusetiawan!

This is really interesting! I reviewed your gist and it looks compatible with the current package (v1.0.6) - operators and helpers align.

The typed path inference with dot-path-value would be a great DX improvement. I'll review it more thoroughly and consider adding it as a separate entry point (e.g., rule-engine-js/typed).

Thanks a lot ❤️

[hyusetiawan]

Glad to be of help! What's the reason to have it in a separate path "/typed"? Because the typing should just augment without breaking?

…

On Sun, Dec 21, 2025 at 7:59 PM crafts69.guy ***@***.***> wrote: *crafts69guy* left a comment (crafts69guy/rule-engine-js#4) <#4 (comment)> Hi @hyusetiawan <https://github.com/hyusetiawan>! This is really interesting! I reviewed your gist and it looks compatible with the current package (v1.0.6) - operators and helpers align. The typed path inference with dot-path-value would be a great DX improvement. I'll review it more thoroughly and consider adding it as a separate entry point (e.g., rule-engine-js/typed). Thanks a lot ❤️ — Reply to this email directly, view it on GitHub <#4 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAIDQCC67SPY6G3UPNQKGFT4C5UBPAVCNFSM6AAAAACN2LWYNKVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTMOBQGMZTAMBXGU> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[crafts69guy]

Hi @hyusetiawan!

You're right - a separate entry point isn't necessary.

To maintain zero dependencies, I'll inline the Path<T> and PathValue<T, P> types directly (~40 lines, no runtime code, from Thanks g-makarov) This keeps everything working out of the box without extra installs.

Thanks for the gist - I'll use it as the foundation! 🙏

[lbineau]

Hi @crafts69guy and happy new year!
Just a heads up on my side, I've updated the library as you suggested and it seems to fix the issue :-)
Many thanks.