Coming from json-logic-js

json-logic-js is the reference JSONLogic implementation. datalogic-rs passes the same official JSONLogic test suite, so your existing rules run unchanged. What changes is the call surface (one function per binding) and a few configurable behaviors. This page is the short version; see How It Compares for the positioning.

The one-liner

json-logic-js:

import jsonLogic from 'json-logic-js';
jsonLogic.apply({ ">": [{ var: "age" }, 18] }, { age: 21 }); // true

datalogic-rs (Node, native binding):

import { apply } from '@goplasmatic/datalogic-node';
apply({ ">": [{ var: "age" }, 18] }, { age: 21 }); // true

datalogic-rs (browser / WASM): the WASM binding is string-in, string-out.

import init, { evaluate } from '@goplasmatic/datalogic-wasm';
await init();
evaluate('{">": [{"var": "age"}, 18]}', '{"age": 21}', false); // "true"

Same rule, same result. For repeated evaluation of one rule, compile it once (Engine/CompiledRule) instead of calling the one-shot helper in a loop.

Custom operations

json-logic-js registers operations globally:

jsonLogic.add_operation("double", (a) => a * 2);

datalogic-rs registers them per engine, and the callback works in JSON (pre-evaluated arguments as a JSON-array string, result as a JSON string):

import { Engine } from '@goplasmatic/datalogic-node';
const engine = new Engine({}, {
  double: (argsJson) => String(JSON.parse(argsJson)[0] * 2),
});

See each binding’s “Custom operators” section for the exact shape.

Behavioral differences to know

datalogic-rs’s defaults are slightly stricter than json-logic-js’s, and are configurable. The two you are most likely to notice:

• Cross-type loose equality. By default datalogic-rs raises on comparisons that json-logic-js would silently resolve to false (for example an object compared to a number). For json-logic-js-classic behavior, build the engine with loose_equality_errors = false.
• Division by zero. datalogic-rs is configurable (ReturnSaturated by default, or ReturnNull / ThrowError / ReturnInfinity); integer division by zero always errors. Pick the division_by_zero mode that matches your expectations.

Both live on EvaluationConfig; see Configuration.

Extensions you gain

Beyond the JSONLogic baseline, datalogic-rs adds opt-in operators the reference engine does not ship: datetime arithmetic, string helpers (length, starts_with, split, …), sort/slice, try/throw, switch, and flagd-compatible feature-flag operators (fractional, sem_ver). In the Rust crate these sit behind Cargo features; every language binding enables them all. See the operator overview.