Registry / web-framework / esbuild-dev-router

esbuild-dev-router

library0.8.0jsnpmunverified

Express middleware for development with esbuild. Bundles TypeScript/JavaScript source files in memory, serves them directly, and automatically reloads the browser on file changes via Server-Sent Events. Current stable version is 0.8.0. Peer dependency on esbuild >0.17. Key differentiators: zero-config live reload injection, no disk writes, mounts as Express Router, merges loader and plugin configs so you can extend defaults. Best for teams that already use Express and esbuild and want a lightweight dev server without Webpack or Vite.

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npm install esbuild-dev-router

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INSTALL

IMPORT

SIG · ESBUILD-DEV-ROUTER

esbuild-dev-router

web-frameworkjavascriptv0.8.0

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

default (devRouter)

✓ import devRouter from 'esbuild-dev-router'

✗ const devRouter = require('esbuild-dev-router')

ESM-only; in TypeScript, you can also use the named export 'devRouter'

devRouter (named)

✓ import { devRouter } from 'esbuild-dev-router'

✗ import devRouter from 'esbuild-dev-router'

Both default and named exports point to the same function. The named export may be easier in some bundler setups.

BuildOptions

✓ import { BuildOptions } from 'esbuild-dev-router'

Re-exports esbuild's BuildOptions type for convenience. Use it to type your config object.

Sets up a basic Express dev server with esbuild-dev-router, bundling src/index.ts into memory and serving static files from public/.

import express from 'express'; import devRouter from 'esbuild-dev-router'; import { resolve } from 'path'; const app = express(); const port = process.env.PORT ?? 5000; app.use(devRouter({ entryPoints: [resolve(process.cwd(), 'src/index.ts')], outdir: resolve(process.cwd(), 'dist'), // used for path resolution only })); app.use(express.static(resolve(process.cwd(), 'public'))); app.listen(port, () => { console.log(`Dev server running on http://localhost:${port}`); });

Debug

Known issues

breakingMust be mounted at root path — the SSE reloader endpoint is hardcoded to '/reloader'.

fix

Mount at app root: app.use(devRouter({...})). Do NOT mount under a subpath like '/assets'.

affects: >=0.0.0

deprecatedThe 'write' option is always forced to false and cannot be overridden.

fix

Remove any 'write' option from the config; it does nothing.

affects: >=0.0.0

gotchaDefaults merge for 'loader', 'plugins', and 'inject' but other options replace defaults.

fix

If you provide 'loader', your entries are added alongside .png and .jpg defaults. For other options, your value completely overrides the default.

affects: >=0.0.0

gotchaNode.js 18+ required. Older Node versions may fail due to modern APIs used internally.

fix

Upgrade Node.js to version 18 or later.

affects: >=0.0.0

gotchaEntry point output filename determines the URL path. E.g., 'src/index.ts' produces '/index.js' and '/index.css'.

fix

Reference the bundled file in HTML as '/index.js' (strip the directory and ts extension).

affects: >=0.0.0

Errors

Common errors & fixes

Error: The reloader endpoint is not found at /assets/reloader

Middleware mounted at a subpath (e.g., app.use('/assets', devRouter(...))) but reloader path is hardcoded to '/reloader'.

fix

Mount the router at the root: app.use(devRouter({...}))

TypeError: Cannot read properties of undefined (reading 'build')

esbuild peer dependency not installed or version <0.17.

fix

Install esbuild >=0.17: npm install -D esbuild

Error: esbuild-dev-router is ESM-only, require() is not supported

Using CommonJS require() to load the package.

fix

Use ESM imports (import devRouter from 'esbuild-dev-router') or enable ESM in your project.

Build failed: No entry point provided

Missing or empty 'entryPoints' option in the config.

fix

Provide an entryPoints array: devRouter({ entryPoints: ['src/index.ts'] })

Upgrade

Version history

0.8.0latest on npm

Audit

Dependencies

esbuildoptionalpeer dependency; >=0.17 is required for the esbuild API used internally

Agent activity

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Resources

githubhttps://github.com/zoisgr/esbuild-dev-router ↗

packagehttps://www.npmjs.com/package/esbuild-dev-router ↗