Depcheck is a tool for analyzing the dependencies in a project to see: how each dependency is used, which dependencies are useless, and which dependencies are missing from package.json.
npm install -g depcheck
Or simply using npx which is a package runner bundled in npm:
$ npx depcheck
Notice: depcheck needs node.js >= 10.
Depcheck not only recognizes the dependencies in JavaScript files, but also supports these syntaxes:
- JavaScript (ES5, ES6 and ES7)
- React JSX
- CoffeeScript
- TypeScript (with
typescriptdependency) - SASS and SCSS
- Vue.js (with
@vue/compiler-sfcdependency)
To get the syntax support by external dependency, please install the corresponding package explicitly. For example, for TypeScript user, install depcheck with typescript package:
npm install -g depcheck typescript
The special component is used to recognize the dependencies that are not generally used in the above syntax files. The following scenarios are supported by specials:
babel- Babel presets and pluginsbin- Dependencies used in npm commands, Travis scripts or other CI scriptscommitizen- Commitizen configuration adaptoreslint- ESLint configuration presets, parsers and pluginsfeross-standard- Feross standard format parsergatsby- Gatsby configuration parsergulp-load-plugins- Gulp-load-plugins lazy loaded pluginshusky- Husky configuration parseristanbul- Istanbul nyc configuration extensionsjest- Jest properties in Jest Configurationkarma- Karma configuration frameworks, browsers, preprocessors and reporterslint-staged- Lint-staged configuration parsermocha- Mocha explicit required dependenciesprettier- Prettier configuration moduletslint- TSLint configuration presets, parsers and pluginsttypescript- ttypescript transformerswebpack- Webpack loadersserverless- Serverless plugins
The logic of a special is not perfect. There might be false alerts. If this happens, please open an issue for us.
depcheck [directory] [arguments]
The directory argument is the root directory of your project (where the package.json file is). If unspecified, defaults to current directory.
All of the arguments are optional:
--ignore-bin-package=[true|false]: A flag to indicate if depcheck ignores the packages containing bin entry. The default value is false.
--skip-missing=[true|false]: A flag to indicate if depcheck skips calculation of missing dependencies. The default value is false.
--json: Output results in JSON. When not specified, depcheck outputs in human friendly format.
--oneline: Output results as space separated string. Useful for copy/paste.
--ignores: A comma separated array containing package names to ignore. It can be glob expressions. Example, --ignores="eslint,babel-*".
--ignore-dirs: DEPRECATED, use ignore-patterns instead. A comma separated array containing directory names to ignore. Example, --ignore-dirs=dist,coverage.
--ignore-path: Path to a file with patterns describing files to ignore. Files must match the .gitignore spec. Example, --ignore-path=.eslintignore.
--ignore-patterns: Comma separated patterns describing files to ignore. Patterns must match the .gitignore spec. Example, --ignore-patterns=build/Release,dist,coverage,*.log.
--quiet: Suppress the "No depcheck issue" log. Useful in a monorepo with multiple packages to focus only on packages with issues.
--help: Show the help message.
--parsers, --detectors and --specials: These arguments are for advanced usage. They provide an easy way to customize the file parser and dependency detection. Check the pluggable design document for more information.
--config=[filename]: An external configuration file (see below).
Depcheck can be used with an rc configuration file. In order to do so, create a .depcheckrc file in your project's package.json folder, and set the CLI keys in YAML, JSON, and JavaScript formats.
For example, the CLI arguments --ignores="eslint,babel-*" --skip-missing=true would turn into:
.depcheckrc
ignores: ["eslint", "babel-*"]
skip-missing: true
Important: if provided CLI arguments conflict with configuration file ones, the CLI ones will take precedence over the rc file ones.
The rc configuration file can also contain the following extensions: .json, .yaml, .yml.
Similar options are provided to depcheck function for programming:
import depcheck from 'depcheck';
const options = {
ignoreBinPackage: false, // ignore the packages with bin entry
skipMissing: false, // skip calculation of missing dependencies
ignorePatterns: [
// files matching these patterns will be ignored
'sandbox',
'dist',
'bower_components',
],
ignoreMatches: [
// ignore dependencies that matches these globs
'grunt-*',
],
parsers: {
// the target parsers
'**/*.js': depcheck.parser.es6,
'**/*.jsx': depcheck.parser.jsx,
},
detectors: [
// the target detectors
depcheck.detector.requireCallExpression,
depcheck.detector.importDeclaration,
],
specials: [
// the target special parsers
depcheck.special.eslint,
depcheck.special.webpack,
],
package: {
// may specify dependencies instead of parsing package.json
dependencies: {
lodash: '^4.17.15',
},
devDependencies: {
eslint: '^6.6.0',
},
peerDependencies: {},
optionalDependencies: {},
},
};
depcheck('/path/to/your/project', options).then((unused) => {
console.log(unused.dependencies); // an array containing the unused dependencies
console.log(unused.devDependencies); // an array containing the unused devDependencies
console.log(unused.missing); // a lookup containing the dependencies missing in `package.json` and where they are used
console.log(unused.using); // a lookup indicating each dependency is used by which files
console.log(unused.invalidFiles); // files that cannot access or parse
console.log(unused.invalidDirs); // directories that cannot access
});The following example checks the dependencies under /path/to/my/project folder:
$> depcheck /path/to/my/project
Unused dependencies
* underscore
Unused devDependencies
* jasmine
Missing dependencies
* lodashIt figures out:
- The dependency
underscoreis declared in thepackage.jsonfile, but not used by any code. - The devDependency
jasmineis declared in thepackage.jsonfile, but not used by any code. - The dependency
lodashis used somewhere in the code, but not declared in thepackage.jsonfile.
Please note that, if a subfolder has a package.json file, it is considered another project and should be checked with another depcheck command.
The following example checks the same project, however, outputs as a JSON blob. Depcheck's JSON output is in one single line for easy pipe and computation. The json command after the pipe is a node.js program to beautify the output.
$> depcheck /path/to/my/project --json | json
{
"dependencies": [
"underscore"
],
"devDependencies": [
"jasmine"
],
"missing": {
"lodash": [
"/path/to/my/project/file.using.lodash.js"
]
},
"using": {
"react": [
"/path/to/my/project/file.using.react.jsx",
"/path/to/my/project/another.file.using.react.jsx"
],
"lodash": [
"/path/to/my/project/file.using.lodash.js"
]
},
"invalidFiles": {
"/path/to/my/project/file.having.syntax.error.js": "SyntaxError: <call stack here>"
},
"invalidDirs": {
"/path/to/my/project/folder/without/permission": "Error: EACCES, <call stack here>"
}
}- The
dependencies,devDependenciesandmissingproperties have the same meanings in the previous example. - The
usingproperty is a lookup indicating each dependency is used by which files. - The value of
missingandusinglookup is an array. It means the dependency may be used by many files. - The
invalidFilesproperty contains the files having syntax error or permission error. The value is the error details. However, only one error is stored in the lookup. - The
invalidDirsproperty contains the directories having permission error. The value is the error details.
Depcheck just walks through all files and tries to find the dependencies according to some predefined rules. However, the predefined rules may not be enough or may even be wrong.
There may be some cases in which a dependency is being used but is reported as unused, or a dependency is not used but is reported as missing. These are false alert situations.
If you find that depcheck is reporting a false alert, please open an issue with the following information to let us know:
- The output from
depcheck --jsoncommand. Beautified JSON is better. - Which dependencies are considered as false alert?
- How are you using those dependencies, what do the files look like?
We use the GitHub release page to manage changelog.
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MIT License.
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