# @putout/plugin-remove-useless-variables [![NPM version][NPMIMGURL]][NPMURL]

[NPMIMGURL]: https://img.shields.io/npm/v/@putout/plugin-remove-useless-variables.svg?style=flat&longCache=true
[NPMURL]: https://npmjs.org/package/@putout/plugin-remove-useless-variables "npm"

🐊[**Putout**](https://github.com/coderaiser/putout) plugin adds ability to find and remove `useless variables`. Renamed to [`@putout/plugin-variables`](https://www.npmjs.com/package/@putout/plugin-variables).

## Install

```
npm i @putout/plugin-remove-useless-variables -D
```

## Rules

- ✅ [assignment](#assignmentn);
- ✅ [declaration](#declaration);
- ✅ [destruct](#destruct);
- ✅ [duplicate](#duplicate);
- ✅ [remove](#remove);
- ✅ [rename](#rename);

## Config

```json
{
    "rules": {
        "remove-useless-variables/assignment": "on",
        "remove-useless-variables/rename": "on",
        "remove-useless-variables/remove": "on",
        "remove-useless-variables/destruct": "on",
        "remove-useless-variables/declaration": ["on", {
            "maxLength": 20
        }],
        "remove-useless-variables/duplicate": "on"
    }
}
```

## assignment

Checkout in 🐊[**Putout Editor**](https://putout.cloudcmd.io/#/gist/a2f7fe5e2c294443576f95dce6fde67e/0699ccb4f7335e8e3f80de891913a8e3ad4f35e3).

### ❌ Example of incorrect code

```js
while (!(files = readDirectory(parentDir)).length) {}
```

### ✅ Example of correct code

```js
while (!readDirectory(parentDir).length) {}
```

## rename

### ❌ Example of incorrect code

```js
function hi(a) {
    const b = a;
}
```

### ✅ Example of correct code

```js
function hi(b) {}
```

## destruct

### ❌ Example of incorrect code

```js
function hi(c) {
    const {a, b} = c;
}
```

### ✅ Example of correct code

```js
function hi({a, b}) {}
```

## remove

### ❌ Example of incorrect code

```js
const child_process = require('node:child_process');

const {exec, spawn} = child_process;
```

### ✅ Example of correct code

```js
const {exec, spawn} = require('node:child_process');
```

### remove

Check it out in 🐊[**Putout Editor**](https://putout.cloudcmd.io/#/gist/041767876a6d41c82260b293a06c2b6b/addf2b49cf9235d9b7a1017065cec5dece232660).

### ❌ Example of incorrect code

```js
const a = 5;
const b = a;

const c = 5;

d = c;
```

### ✅ Example of correct code

```js
const b = 5;

d = 5;
```

### declaration

Check it out in 🐊[**Putout Editor**](https://putout.cloudcmd.io/#/gist/32177535829956ef4c7b51587a8853c3/1fe071ff6542dc66ffad55f4776733903ab07241).

### ❌ Example of incorrect code

```js
function x() {
    const a = 5;
    return a;
}

const z = b.c.replace('x', 'y');

b.c = z;
```

### ✅ Example of correct code

```js
function x() {
    return 5;
}

b.c = b.c.replace('x', 'y');
```

### duplicate

Check it out in 🐊[**Putout Editor**](https://putout.cloudcmd.io/#/gist/32177535829956ef4c7b51587a8853c3/52f19ab0e467ad7cc54fa8c554c3b0804de9d1ca).

### ❌ Example of incorrect code

```js
const DestructuringErrors = function DestructuringErrors(a, b) {
    return [a, b];
};
```

### ✅ Example of correct code

```js
function DestructuringErrors(a, b) {
    return [a, b];
}

bc = b.c.replace('x', 'y');
```

## License

MIT