jlens-wasm

JSONata for the browser, compiled from Rust to WebAssembly. It evaluates expressions, explains how a result was reached, and gives editors completion, diagnostics and hover driven by a JSON Schema inferred from sample documents.

This is an ES module for browsers (--target web). It also runs in Node.js 20+ and Deno if you pass the .wasm bytes to init.

Try it in the web editor, which is built on this package, and read the jlens book for the language and the API.

import init, { Expression } from "jlens-wasm";

await init(); // fetches jlens_bg.wasm next to jlens.js

const expr = new Expression("$sum(items[type = $kind].(price * qty))");
expr.evaluate({ items: [{ type: "a", price: 2.5, qty: 4 }] }, { kind: "a" }); // 10

API

| Export | Purpose | |---|---| | init(options?) | Loads the WebAssembly module; call (and await) it once before anything else | | new Expression(source) | Compiles an expression; throws a JlensError on syntax errors | | expr.evaluate(input?, bindings?, options?) | Evaluates against a JSON-compatible value; undefined when the result is undefined | | expr.evaluateJson(json?, bindings?, options?) | The same with JSON text in and out (faster for large documents) | | new Document(input), Document.fromJson(text) | A document converted once, for expr.evaluateDocument(doc, bindings?, options?) | | expr.evaluateWithAudit(input?, bindings?, options?) | Result, audit tree and explanation; errors are reported, not thrown | | expr.ast() | The processed syntax tree | | parseRecover(source) | Partial syntax tree and every diagnostic, without throwing | | inferSchema(samples, overrides?) | A JSON Schema (2020-12) inferred from sample documents | | new LanguageService(schema?, variables?) | complete, diagnostics, hover and signatureHelp for an editor | | functions() | The built-in function catalog | | version() | The jlens version |

options takes timeout (milliseconds) and maxDepth; for evaluateWithAudit also level ("off", "decisions", "full") and limits. Errors are Error objects named JlensError with the JSONata error code, plus position, start, end and token when known.

All offsets, in both directions, are UTF-16 code units, like JavaScript string indexes.

The full guide is the WebAssembly chapter of the jlens book.

License

MIT. The code and documentation ported or adapted from JSONata are also under the MIT license; see LICENSE.