This is the unpublished documentation of wasm-pack, the published documentation is available on the main Rust and WebAssembly documentation site . Features documented here may not be available in released versions of wasm-pack.


Currently, wasm-pack generated npm modules require us to you have fetch polyfill in your node project.

If there is a module from wasm-pack build --target nodejs you may encounter some errors regarding global Headers, Request, Response and fetch Web APIs.

Common errors:

ReqwestError(reqwest::Error { kind: Builder, source: "JsValue(ReferenceError: Headers is not defined
ReqwestError(reqwest::Error { kind: Builder, source: "JsValue(ReferenceError: Request is not defined

    var ret = getObject(arg0) instanceof Response;
ReferenceError: Response is not defined


Import or declare fetch and objects: Headers, Request, Response

// CommonJS
const fetch = require('node-fetch');

// ES Module
import fetch from 'node-fetch';

// @ts-ignore
global.fetch = fetch;
// @ts-ignore
global.Headers = fetch.Headers;
// @ts-ignore
global.Request = fetch.Request;
// @ts-ignore
global.Response = fetch.Response;