Putout [![NPM version][NPMIMGURL]][NPMURL] [![Build Status][BuildStatusIMGURL]][BuildStatusURL] [![Coverage Status][CoverageIMGURL]][CoverageURL]

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[NPMURL]: https://npmjs.org/package/putout "npm"
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> **Perfection is finally attained not when there is no longer anything to add,
> but when there is no longer anything to take away.**
>
> (c) Antoine de Saint Exupéry

!putout

🐊Putout is a JavaScript Linter, pluggable and configurable code transformer, drop-in ESLint replacement with built-in code printer and ability to fix syntax errors. It has a lot of transformations that keeps your codebase in a clean state, removing any code smell and making code readable according to best practices.

The main target is JavaScript, but:

- ✅ JSX;
- ✅ TypeScript;
- ✅ Yaml;
- ✅ Markdown;
- ✅ JSON;
- ✅ Ignore;

are also supported. Here is how it looks like:


🤷‍️ In doubt about using 🐊Putout?

Check out couple variants of plugins that does the same: linting debugger statement:

- ❌ SWCLint no-debugger: 49 lines;
- ❌ RSLint no-debugger: 48 lines;
- ❌ ESLint no-debugger: 43 lines;
- ❌ Rome no-debugger: 28 lines;
- ✅ 🐊Putout remove-debugger: 7 lines:

``js
'use strict';

module.exports.report = () => Avoid 'debugger' statement;

module.exports.replace = () => ({
debugger: '',
});
`

Choose wisely, competitors cannot even fix… 🤫

🙏 Whom should I thank for this project exist?

> If I have seen further, it is by standing upon the shoulders of giants.
>
> (c) Isaak Newton

- 💪 ESLint for stable releases and future proof API.
- 💪 Babel for amazing API documented in Handbook and responsiveness of a team.
- 💪 Prettier for minimalistic options and uniform codestyle.
- 💪 jscodeshift for making codemods simple and popular.

🤷 Why does this project exist?

- ❌ ESLint avoids fixes that could change the runtime behavior.
- ❌ Babel produces throw-away code.
- ❌ Prettier is a formatter.
- ❌ jscodeshift has no config and plugins support.

☝️ 🐊Putout on the other hand can make more drastic code transformations that directly affects your codebase making it a better place to code 💻.

It can:

- ✅ remove unused variables;
- ✅ remove unused for-of variables;
- ✅ remove unused typescripts types;
- ✅ remove unreferenced variables;
- ✅ remove unused private fields;
- ✅ remove unused expressions;
- ✅ remove useless variables;
- ✅ remove useless Object.assign();
- ✅ remove useless replace();
- ✅ remove useless map;
- ✅ remove useless mapped types;
- ✅ remove useless mapping modifiers;
- ✅ remove useless continue;
- ✅ remove useless operand;
- ✅ remove useless array constructor;
- ✅ remove useless conditions;
- ✅ remove useless type conversion;
- ✅ remove useless functions;
- ✅ remove useless Array.from;
- ✅ remove useless spread;
- ✅ remove useless arguments;
- ✅ remove useless escape;
- ✅ remove useless async;
- ✅ remove useless await;
- ✅ remove useless typeof;
- ✅ remove useless template expressions;
- ✅ remove useless for-of;
- ✅ remove useless array.entries();
- ✅ remove debugger statement;
- ✅ remove iife;
- ✅ remove nested blocks;
- ✅ remove process.exit call;
- ✅ remove console.log calls;
- ✅ remove empty block statements;
- ✅ remove empty patterns;
- ✅ remove strict mode directive from esm;
- ✅ remove constant conditions;
- ✅ remove boolean from assertion;
- ✅ remove boolean from logical expressions;
- ✅ remove duplicates from TypeScript Union;
- ✅ remove unreachable code;
- ✅ remove duplicate keys;
- ✅ remove useless typescripts types;
- ✅ remove duplicate typescripts interface keys;
- ✅ replace test.only to test calls;
- ✅ replace test.skip to test calls;
- ✅ reuse duplicate init;
- ✅ split variable declarations;
- ✅ split nested destructuring;
- ✅ simplify assignment;
- ✅ simplify ternary;
- ✅ simplify logical expressions;
- ✅ if absent strict mode directive in commonjs add it;
- ✅ convert const to let (when needed to avoid TypeError);
- ✅ convert apply to spread;
- ✅ convert bitwise to logical operator;
- ✅ convert concat to flat;
- ✅ convert esm to commonjs (enabled for *.cjs);
- ✅ convert commonjs to esm (enabled for *.mjs);
- ✅ convert template with one expression to string;
- ✅ convert equal to strict equal;
- ✅ convert indexOf to includes;
- ✅ convert replace to replaceAll;
- ✅ convert assignment to arrow function;
- ✅ convert forEach to for...of;
- ✅ convert map to for...of;
- ✅ convert reduce to for...of;
- ✅ convert Math.sqrt() to Math.hypot();
- ✅ extract sequence expressions;
- ✅ extract object properties;
- ✅ add return await;
- ✅ remove useless Promise.resolve;
- ✅ convert Promise.reject to throw;
- ✅ declare before reference;
- ✅ declare undefined variables;
- ✅ declare imports first;
- ✅ apply as type assertions;
- ✅ apply utility types;
- ✅ apply array.at;
- ✅ apply filter(Boolean);
- ✅ apply isArray;
- ✅ apply if condition;
- ✅ apply await import;
- ✅ apply comparison order;
- ✅ apply flatMap();
- ✅ apply template literals;
- ✅ merge duplicate imports;
- ✅ merge duplicate functions;

Install

`
npm i putout -D
`

Usage

`
Usage: putout [options] [path]
Options:
-h, --help display this help and exit
-v, --version output version information and exit
-f, --format [formatter] use a specific output format, the default is: 'progress-bar' locally and 'dump' on CI
-s, --staged add staged files when in git repository
-i, --interactive set lint options using interactive menu
--fix apply fixes of errors to code
--fix-count [count = 10] count of fixes rounds
--rulesdir use additional rules from directory
--transform [replacer] apply Replacer, for example 'var __a = __b -> const __a = __b', read about Replacer https://git.io/JqcMn
--plugins [plugins] a comma-separated list of plugins to use
--enable [rule] enable the rule and save it to '.putout.json' walking up parent directories
--disable [rule] disable the rule and save it to '.putout.json' walking up parent directories
--enable-all enable all found rules and save them to '.putout.json' walking up parent directories
--disable-all disable all found rules (set baseline) and save them to '.putout.json' walking up parent directories
--match [pattern] read '.putout.json' and convert 'rules' to 'match' according to 'pattern'
--fresh generate a fresh cache
--no-config avoid reading '.putout.json'
--no-ci disable the CI detection
--no-cache disable the cache
--no-worker disable worker thread
`

To find errors:

`
putout lib test
`

To fix errors:

`
putout lib test --fix
`

Plugins

By default 🐊Putout uses all enabled by default plugins, anyways it can be run with a couple mentioned plugins (split with ","):

`sh
putout lib --plugins remove-debugger,remove-unused-variables
`

Environment variables

🐊Putout supports next environment variables:

- PUTOUT_FILES - files that should be processed by putout, divided by ",";
- PUTOUT_CONFIG_FILE - path to 🐊Putout config file;
- ESLINT_CONFIG_FILE - path to ESLint config file;
- NO_ESLINT - do not run ESLint after 🐊Putout;
- NO_ESLINT_WARNINGS - do not show ESLint warnings;

`sh
PUTOUT_FILES=lib,test putout --fix
`

Configuration

To configure create .putout.json file and override any of default options.

$3

When you need to match paths to rules you can use match section for this purpose in .putout.json:

`json
{
"match": {
"server": {
"remove-process-exit": true
}
}
}
`

$3

When you need to ignore some routes no metter what, you can use ignore section in .putout.json:

`json
{
"ignore": ["test/fixture"]
}
`

Plugins

🐊Putout supports two types of plugins, prefix with:

- ✅ @putout/plugin-;
- ✅ putout-plugin-;

To use your plugin createnpm package with keywords putout, putout-plugin and add it to .putout.json.

For example if you need to remove-something create 🐊Putout plugin with name putout-plugin-remove-something and it to package.json:

`json
{
"plugins": ["remove-something"]
}
`

Codemods

🐊Putout supports codemodes in the similar to plugins way, just create a directory ~/.putout and put your plugins there. Here is example: convert-tape-to-supertape and this is examples of work.

API

All examples works both in ESM and CommonJS.

CommonJS:

`js
const {putout} = require('putout');
`

ESM:

`js
import {putout} from 'putout';
`

$3

`js
import {putout} from 'putout';

const source =
const t = 'hello';
const m = t + '!';
console.log(t);
;

putout(source, {
plugins: ['remove-unused-variables'],
});

// returns

const t = 'hello';
console.log(t);
;
`

$3

`js
import {putoutAsync} from 'putout';

const source =
const t = 'hello';
const m = t + '!';
console.log(t);
;

await putoutAsync(source, {
plugins: ['remove-unused-variables'],
});

// returns

const t = 'hello';
console.log(t);
;
``

License

MIT