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# prefer-object-from-entries

[Added in v0.10.1](https://github.com/web-infra-dev/rslint/releases/tag/v0.10.1)
## Configuration


```ts title=rslint.config.ts
import { defineConfig, unicornPlugin } from '@rslint/core';

export default defineConfig([
  unicornPlugin.configs.recommended,
  {
    rules: {
      'unicorn/prefer-object-from-entries': 'error',
    },
  },
]);
```

## Rule details

Prefer `Object.fromEntries()` when converting key-value pairs into an object.
The rule checks simple `reduce()` callbacks, an empty object followed by a
`for…of` loop that assigns each pair, and calls to `_.fromPairs()` or
`lodash.fromPairs()`.

Examples of **incorrect** code for this rule:

```javascript
const first = pairs.reduce(
  (object, [key, value]) => ({ ...object, [key]: value }),
  {},
);

const second = pairs.reduce(
  (object, [key, value]) => Object.assign(object, { [key]: value }),
  {},
);

const third = {};
for (const [key, value] of pairs) {
  third[key] = value;
}

const fourth = _.fromPairs(pairs);
```

Examples of **correct** code for this rule:

```javascript
const object = Object.fromEntries(pairs);
```

Automatic fixes preserve the mapped key and value. Reductions with an
accumulator used elsewhere in the callback, known non-array receivers, and
null-prototype accumulators such as `Object.create(null)` are ignored.
Non-computed `__proto__` properties are also ignored because converting them
would change how the object's prototype is set.

Comments that would be removed prevent automatic fixes. A reduction with
explicit TypeScript type arguments is reported without a fix.

## Options

### functions

Type: `string[]`\
Default: `[]`

Add names or dotted paths of functions that convert pairs into an object.
`_.fromPairs()` and `lodash.fromPairs()` are always checked.

```json
{
  "unicorn/prefer-object-from-entries": [
    "error",
    { "functions": ["getObjectFromKeyValue", "utils.fromPairs"] }
  ]
}
```

With this configuration, `utils.fromPairs(pairs)` is reported and fixed to
`Object.fromEntries(pairs)`.

## Differences from upstream

- Autofixes for `reduce()` use `.flatMap()` to skip missing elements in sparse
  arrays. A reduction over `[1, , 3]` still uses the original indices `0` and `2`.
- TypeScript callbacks with a declared return type are reported without a fix.
  A return type such as `Record<string, number>` describes the accumulator.
  When converting the callback manually, update the return type to match the
  array of key-value pairs returned by the new callback.

## Original documentation

- [eslint-plugin-unicorn: prefer-object-from-entries](https://github.com/sindresorhus/eslint-plugin-unicorn/blob/v79.0.0/docs/rules/prefer-object-from-entries.md)
- [Source code](https://github.com/sindresorhus/eslint-plugin-unicorn/blob/v79.0.0/rules/prefer-object-from-entries.js)