ESM hot-reloading for Node.js
hot ./server.jsInstall hot-esm by running
yarn add hot-esmhot-esm provides a loader that clears the module cache for files that are edited and the files that import them. This allows you to re-import your application and get updated code.
node --experimental-loader hot-esm ./server.js
# Or use this shorthand:
hot ./server.jsimport * as http from 'http'
const server = http.createServer(async (request, response) => {
const app = await import('./app.js')
app.default(request, response)
})
server.listen(8080)You'll have to find an appropriate place in your application to place an
import() expression. This expression needs to run often enough to not miss
updates.
State that is local to a file will be lost when that file is re-imported. To
share state between the old and new copies of a file, put that state in
global.
Also, any ongoing side-effects will need to be cleaned up when a new version of
a file is imported. Otherwise, for example, multiple of the same event listener
will be running. Again, this can be managed using global state.
Note that this only works with ECMAScript Modules and not with CommonJS modules.
Also, edits to files in node_modules, even if they are ECMAScript Modules are
ignored by default as attaching filesystem watchers to so many directories is
too expensive.
But, specific packages inside of node_modules can be watched for updates by
setting the environment variable:
HOT_INCLUDE_PACKAGES=package1,package2hot-esm provides debug logging detailing which files are watched, when they get invalidated, and when they get re-imported. Those logs can be enabled by setting the environment variable:
DEBUG=hot-esm