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babel-watch
Advanced tools
Reload your babel-node app on JS source file changes. And do it *fast*.
Reload your babel-node app on JS source file changes. And do it fast.
If you're tired of using babel-node
together with nodemon
, babel/cli
with --watch
option (or similar solution). The reason why the aforementioned setup performs so badly is the startup time of babel-node
itself. babel-watch
only starts babel
in the "master" process where it also starts the file watcher. The transpilation is performed in that process too. On file-watcher events, it spawns a pure node
process and passes transpiled code from the parent process together with the source maps. This allows us to avoid loading babel
and all its deps every time we restart the JS script/app.
A unique feature of babel-watch
is capability of automatically detecting files that needs to be watched. You no longer need to specify the list of files or directories to watch for. With "autowatch" the only thing you need to do is to pass the name of your main script and babel-watch
will start watching for the changes on files that are loaded by your node program while it is executing. (You can disable autowatch with -D
option or exclude some directories from being watched automatically with -x
).
Currently babel-watch
is supported on Linux, OSX and Windows.
Just install it and add to your package:
With NPM:
npm install --save-dev babel-watch
With Yarn:
yarn add --dev babel-watch
(Make sure you have @babel/core
installed as dependency in your project as babel-watch
only defines @babel/core
as a "peerDependency")
Then use babel-watch
in your package.json
in scripts section like this:
"scripts": {
"start": "babel-watch src/main.js"
}
babel-watch
was made to be compatible with babel-node
and nodemon
options. Not all of them are supported yet, here is a short list of supported command line options:
-d, --debug [port] Enable debug mode (deprecated) with optional port
-B, --debug-brk Enable debug break mode (deprecated)
-I, --inspect [address] Enable inspect mode
-X, --inspect-brk [address] Enable inspect break mode
-o, --only [globs] Matching files will *only* be transpiled (default: null)
-i, --ignore [globs] Matching files will not be transpiled, but will still be watched. Default value is "node_modules". If you specify this option and still want to exclude modules, be sure to add it to the list. (default: ["node_modules"])
-e, --extensions [extensions] List of extensions to hook into (default: [".js",".jsx",".es6",".es",".mjs"])
-w, --watch [dir] Watch directory "dir" or files. Use once for each directory or file to watch (default: [])
-x, --exclude [dir] Exclude matching directory/files from watcher. Use once for each directory or file (default: [])
-L, --use-polling In some filesystems watch events may not work correcly. This option enables "polling" which should mitigate this type of issue
-D, --disable-autowatch Don't automatically start watching changes in files "required" by the program
-H, --disable-ex-handler Disable source-map-enhanced uncaught exception handler. You may want to use this option in case your app registers a custom uncaught exception handler
-m, --message [string] Set custom message displayed on restart (default: ">>> Restarting due to change in file(s): %s")
-c, --config-file [string] Babel config file path
--clear-console If set, will clear console on each restart. Restart message will not be shown
--before-restart <command> Set a custom command to be run before each restart, for example "npm run lint"
--restart-timeout <ms> Set the maximum time to wait before forcing a restart. Useful if your app does graceful cleanup. (default: 2000)
--no-colors Don't use console colors
--restart-command <command> Set a string to issue a manual restart. Set to `false` to pass stdin directly to process. (default: "rs")
--no-debug-source-maps When using "--inspect" options, inline source-maps are automatically turned on. Set this option to disable that behavior
-V, --version output the version number
-h, --help display help for command
While the babel-watch
process is running you may type "rs" and hit return in the terminal to force reload the app.
To pass options directly to the Node child that are not shown above, use BABEL_WATCH_NODE_OPTIONS
. For example:
BABEL_WATCH_NODE_OPTIONS="--experimental-worker" babel-watch app.js
Note not to use NODE_OPTIONS
. This will apply the options to both the file watcher and the child process, which may have undesired
effects with certain options like --inspect
.
In most of the cases you would rely on "autowatch" to monitor all the files that are required by your node application. In that case you just run:
babel-watch app.js
If you have your view templates (build with pug, mustache or any other templating library) in the directory called views
, autowatch will not be able to detect changes in view template files (see why) , so you need to pass in that directory name using --watch
option:
babel-watch --watch views app.js
When you want your app not to restart automatically for some set of files, you can use --exclude
option:
babel-watch --exclude templates app.js
Start the debugger
babel-watch app.js --debug 5858
Demo of nodemon + babel-node
(on the left) and babel-watch
reloading simple express
based app:
Using babel-node
or babel-watch
is not recommended in production environment. For the production use it is much better practice to build your node application using babel
and run it using just node
.
babel-watch
's versions now mirror the major version range of the Babel version it is compatible with. Currently, that is 7.x
.
babel-watch >= 2.0.7
(and now 7.x
) is compatible with @babel/core
version 7.0.0
and abovebabel-watch < 2.0.7 && >= 2.0.2
is compatible with babel-core
version 6.5.1
babel-watch <= 2.0.1
is compatible with babel-core
from 6.4.x
up to 6.5.0
(This is due to the babel's "option manager" API change in babel-core@6.5.1
)
--ignore
and --exclude
?These options seem very similar, and so there is some confusion about them. The difference is:
--ignore
will watch the file, but not transpile it with Babel.
--ignore
to mirror the Babel option.--exclude
will not watch the file at all and thus it won't be transpiled either.
--exclude
can really speed things up.If you want to know which file caused a restart, or why a file was not processed, add env DEBUG="babel-watch:*"
before your command to see babel-watch internals. Please do this before filing a bug report.
There are a couple of reasons that could be causing that:
babel-watch
running within docker container and have filesystem mirrored). In that case try running babel-watch
with -L
option which will enable polling for file changes.-x
or --exclude
).You perhaps are using autowatch. Apparently since view templates are not loaded using require
command but with fs.read
instead, therefore autowatch is not able to detect that they are being used. You can still use autowatch for all the js sources, but need to specify the directory name where you keep your view templates so that changes in these files can trigger app restart. This can be done using --watch
option (e.g. babel-watch --watch views app.js
).
babel-watch
does not have @babel/core
listed as a direct dependency but as a "peerDependency". If you're using babel
in your app you should already have @babel/core
installed. If not you should do npm install --save-dev @babel/core
. We decided not to make @babel/core
a direct dependency as in some cases having it defined this way would make your application pull two versions of @babel/core
from npm
during installation and since @babel/core
is quite a huge package that's something we wanted to avoid.
babel-watch
creates a temporary file each time it runs in order to watch for changes. When running as an npm script, this can end up putting these files into your project root. This is due to an issue in npm which changes the value of TMPDIR
to the current directory. To fix this, change your npm script from babel-watch ./src/app.js
to TMPDIR=/tmp babel-watch ./src/app.js
.
regeneratorRuntime is not defined
error when running with babel-watch but babel-node runs just fineThe reason why you're getting the error is because the babel regenerator plugin (that gives you support for async functions) requires a runtime library to be included with your application. You will get the same error when you build your app with babel
first and then run with node
. It works fine with babel-node
because it includes babel-polyfill
module automatically whenever it runs your app, even if you don't use features like async functions (that's one of the reason why its startup time is so long). Please see this answer on stackoverflow to learn how to fix this issue
Try searching over the issues on GitHub here. If you don't find anything that would help feel free to open new issue!
All PRs are welcome!
FAQs
Reload your babel-node app on JS source file changes. And do it *fast*.
We found that babel-watch demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 2 open source maintainers collaborating on the project.
Did you know?
Socket for GitHub automatically highlights issues in each pull request and monitors the health of all your open source dependencies. Discover the contents of your packages and block harmful activity before you install or update your dependencies.
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