@ohm-js/wasm

Compile Ohm.js grammars to WebAsssembly, so they can be used from other languages.

To use the grammar, use the appropriate miniohm package for your language.

NOTE: This package is experimental; the API is not yet stable.

Prerequisites

This package requires Node 24.

Usage (compiling to Wasm)

Command line

npx ohm2wasm my-grammar.ohm

This will write a Wasm grammar blob to ./my-grammar.wasm.

API

import * as ohm from 'ohm-js';
import {Compiler} from '@ohm-js/wasm';

// Instantiate your own grammar…
const g = ohm.grammar('MyGrammar { start = "blah" }');

// compile() returns the Wasm grammar blob as a Uint8Array.
const bytes = new Compiler(g).compile();

Differences:

Arity

• Iter and Opt nodes are no longer flattened.
• Positive lookahead does not bind a node.

Building ASTs

• AstBuilder class replaces toAST.
• Recursive calls: this.toAst(node) rather than node.toAST(this.args.mapping)
• this.currNode vs this.

Development

Prerequisites

• pnpm
• Node >= 24
• Make

Setup

From the repo root:

pnpm install

Testing etc.

From packages/wasm dir:

pnpm test # Run all tests
pnpm ava test/test-liquid-html.js # Run a specific test file
make bench # Run perf benchmarks
node scripts/parseLiquid.js '/Users/pdubroy/dev/third_party/Shopify/dawn/**/*.liquid'