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Fastify plugin for processing Javascript with babel.


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fastify-babel NPM Version

Fastify Babel plugin for development servers

Never load this plugin on production servers

The purpose of this module is for running a test HTTP server directly from sources. Babel transformations are not async and all additional requests are blocked while transformation is in process.

You should always use a build step to install pre-transformed files to production servers.

Install fastify-babel

This module requires node.js 10 or above. It is should normally be used with fastify-static >= 0.12.0. This module requires the local filename to be in payload.filename.

npm i --save-dev fastify-babel @babel/core


'use strict';

const path = require('path');
const fastify = require('fastify')();
const fastifyStatic = require('fastify-static');
const fastifyBabel = require('fastify-babel');

	.register(fastifyStatic, {
		root: path.join(__dirname, 'html/myapp'),
		prefix: '/myapp',
	.register(fastifyStatic, {
		root: path.join(__dirname, 'node_modules'),
		prefix: '/node_modules',
		decorateReply: false,
	.register(fastifyBabel, {
		babelrc: {
			plugins: ['bare-import-rewrite'],
	.listen(3000, '', err => {
		if (err) {
			throw err;
		console.log(`server listening at${fastify.server.address().port}/`);

In addition to fastify-babel this example requires fastify-static and babel-plugin-bare-import-rewrite.



An object provided directly to babel for each request that is processed. Default is empty.


A RegExp object used to match the Content-Type header. Only replies with matching header will be processed by babel. Default /(java|ecma)script/.


Setting this to false will allow the full error message to be displayed. By default errors are masked to prevent disclosure of server details.


A Map-like object for caching transform results. This object must have support for both get and set methods.


A string used to salt the hash of source content.

fastify-babel for enterprise

Available as part of the Tidelift Subscription.

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