noir-js

name	noir-js
description	JavaScript/TypeScript integration with Noir circuits. Covers compilation, witness generation, proving, and verification using noir_js and bb.js.
allowed-tools	Read, Grep, Glob, Edit, Write, Bash

Noir JavaScript/TypeScript Integration

Use @noir-lang/noir_js and @aztec/bb.js to compile, prove, and verify Noir circuits from JavaScript or TypeScript.

Pipeline Overview

1. Compile circuit with nargo compile -- produces a JSON artifact in target/
2. Load the artifact in JavaScript
3. Generate witness with noir_js (Noir class)
4. Create proof with bb.js (UltraHonkBackend)
5. Verify proof on the client or on-chain

Key Packages

Package	Purpose
@noir-lang/noir_js	Witness generation, oracle callbacks, CompiledCircuit type
@aztec/bb.js	Proof generation and verification (UltraHonkBackend, Barretenberg)

The @noir-lang/noir_js package version must match the version of nargo used to compile the circuit.

Quick Start

import { Noir } from "@noir-lang/noir_js";
import { Barretenberg, UltraHonkBackend } from "@aztec/bb.js";
import circuit from "../target/my_circuit.json" with { type: "json" };

// 1. Initialize backend
const api = await Barretenberg.new({ threads: 8 });
const noir = new Noir(circuit as any);
const backend = new UltraHonkBackend(circuit.bytecode, api);

// 2. Generate witness
const inputs = { x: 3, y: 4 };
const { witness } = await noir.execute(inputs);

// 3. Generate proof
const { proof, publicInputs } = await backend.generateProof(witness);

// 4. Verify proof
const isValid = await backend.verifyProof({ proof, publicInputs });
console.log("Proof valid:", isValid);

Input Encoding Rules

All inputs are passed as values matching their Noir types:

Noir Type	JS Encoding	Example
Field	Number or hex string	3 or "0x1a"
u32, i8, etc.	Number or string	255
bool	Boolean or "0"/"1"	true
[Field; N]	JS array of encoded values	[1, 2, 3]
struct	JS object with matching field names	{ x: 1, y: 2 }

Oracle Callbacks

Oracles let the circuit call JavaScript functions during witness generation. Define callbacks matching #[oracle(name)] declarations in Noir:

const oracleCallbacks = {
  async get_secret(key: string[]): Promise<string[]> {
    const secret = await fetchSecretFromDB(key[0]);
    return [secret];
  },
};

const { witness } = await noir.execute(inputs, oracleCallbacks);

Oracle callbacks receive and return string arrays where each string is a field element.

Detailed Guides

• Compilation -- Building circuits and producing JSON artifacts
• Witness Generation -- Executing circuits, input encoding, oracles
• Proving and Verifying -- Proof creation, verification, Solidity verifiers
• Artifact Loading -- Loading artifacts in Node.js and browsers, version compatibility