#prefer-object-from-entries

#Configuration

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:

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:

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.

{
  "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
• Source code