Makes eslint the fastest linter on the planet.
"But eslint is pretty fast already, right?"
Yes, it's really fast. But the node.js startup time and loading all the
required modules slows down linting times for a single file to ~700
eslint_d reduces this overhead by running a server in the
background. It brings the linting time down to ~160 milliseconds. If you want
to lint from within your editor whenever you save a file,
eslint_d is for
This will install the
eslint_d command globally:
$ npm install -g eslint_d
To start the server and lint a file, just run:
$ eslint_d file.js
On the initial call, the
eslint_d server is launched and then the given file
is linted. Subsequent invocations are super fast.
How does this work?
The first time you use
eslint_d, a little server is started in the background
and bound to a random port. You can then run
eslint_d commands the
same way you would use
eslint and it will delegate to the background server.
It will load a separate instance of eslint for each working
directory to make sure settings are kept local. If eslint is found in the
current working directories
node_modules folder, then this version of eslint
is going to be used. Otherwise, the version of eslint that ships with
eslint_d is used as a fallback.
It's possible to force
eslint_d to only resolve local
eslint by setting the
ESLINT_D_LOCAL_ESLINT_ONLY environment variable to a truthy value (ie.
To keep the memory footprint low,
eslint_d keeps only the last 10 used
instances in the internal nanolru cache.
What if eslint or a plugin is updated?
The cached version of eslint and the Node
require cache for the current
working directory are cleared whenever a change to one of these files is
pnpm-lock.yaml. If changes are not automatically detected,
remember to run
eslint_d restart to bounce the background server.
Note: Change detection was switched from mtime to content hash with v12.
Which versions of eslint are supported?
You can use
eslint_d with multiple projects depending on different versions
of eslint. If no local eslint is found,
eslint_d falls back to the eslint
version that ships with
Control the server like this:
$ eslint_d <command>
start: start the server
stop: stop the server
status: print out whether the server is currently running
restart: restart the server
[options] file.js [file.js] [dir]: invoke
eslintwith the given options. The
eslintengine will be created in the current directory. If the server is not yet running, it is started.
eslint_d --help to see the supported
When the server starts,
eslint_d selects a free port automatically
and decides on a random access token. Both the port and token are
written to an
.eslint_d file so that future usages of
connect to the already running server. The
.eslint_d file is stored
XDG_RUNTIME_DIR directory if this environment variable is
defined. If the variable is not defined then the file is stored in the
user's home directory.
WebStorm: Configure your IDE to point to the
eslint_dpackage instead of
eslint. In the ESLint configuration dialog, under 'ESLint package', select your
Emacs: Use flycheck with the
Sublime: The official SublimeLinter-eslint plugin automatically prefers
eslint_dif it finds one.
Atom, VSCode: You will not gain any performance from this module as these editors already cache eslint instances for you.
If you're using
eslint_d in any other editor, please let us know!
eslint_d has an additional flag that
eslint does not have,
--fix-to-stdout which prints the fixed file to stdout. This allows editors to
add before save hooks to automatically fix a file prior to saving. It must be
Vim: Add this to your
.vimrcto lint the current buffer or visual selection on
" Autofix entire buffer with eslint_d: nnoremap <leader>f mF:%!eslint_d --stdin --fix-to-stdout<CR>`F " Autofix visual selection with eslint_d: vnoremap <leader>f :!eslint_d --stdin --fix-to-stdout<CR>gv
Emacs: See eslintd-fix
If the above doesn't autofix: This can happen with .vue files
eslint_d --stdin --fix-to-stdoutto
eslint_d --stdin --fix-to-stdout --stdin-filename %(% = path to file you want to autofix)
In Vim, the above mapping should be replaced with:
nnoremap <leader>f mF:%!eslint_d --stdin --fix-to-stdout --stdin-filename %<CR>`F
If you're really into performance and want the lowest possible latency, talk to
eslint_d server with netcat. This will also eliminate the node.js startup
You first need to extract the port and access token from the
.eslint_d file. The location of this file may change depending on
your system (see above). For example, if
specified, you can do this:
$ PORT=`cat $XDG_RUNTIME_DIR/.eslint_d | cut -d" " -f1` $ TOKEN=`cat $XDG_RUNTIME_DIR/.eslint_d | cut -d" " -f2`
Then, you can do the following to run eslint on
$ echo "$TOKEN $PWD file.js" | nc localhost $PORT
Or if you want to work with stdin:
$ echo "$TOKEN $PWD --stdin" | cat - file.js | nc localhost $PORT
eslint in under
Tip For additional speed, did you know that you can lint only files that
have changed? This is a feature of normal
eslint, but it also works from
$ eslint_d . --cache
If you're interested in building something similar to this: Most of the logic was extracted to core_d, a library that manages the background server.
12.0.0: eslint 4 - 8, node 12 - 16 (ships with eslint 8)
11.0.0: eslint 4 - 8, node 12 - 16 (ships with eslint 7)
10.0.0: eslint 4 - 7, node 10 - 14 (using new
ESLintAPI if available)
9.0.0: eslint 4 - 7, node 10 - 14 (using
8.0.0: eslint 4 - 6, node 8 - 12
7.2.0: eslint 4 - 5, node 6 - 10
7.0.0: eslint 5.4+, node 6, 8 and 10
6.0.0: eslint 5.0+, node 6+ (eslint dropped node 4)
5.0.0: eslint 4.0+
4.0.0: eslint 3.0+, node 4+ (eslint dropped node 0.10 and 0.12)
3.0.0: eslint 2.2+
2.0.0: eslint 1.4+, node 4 (and probably older)