eslint-plugin-prefer-object-spread

1.2.1 verified Sat Apr 25 auth: no javascript maintenance

ESLint rule that flags Object.assign() calls when the target is an object literal, recommending object spread properties instead. Version 1.2.1 is the latest stable release; the package has not been updated since 2016. It applies only when Object.assign() is used for cloning (first argument is an object literal) to avoid false positives when mutating an existing object. Requires ESLint >=0.8.0 and Node >=4.0.0. This plugin is lightweight and has a single rule. It is not actively maintained and may be superseded by built-in ESLint rules or new JavaScript features.

Common errors

error Error: Failed to load plugin 'prefer-object-spread' declared in '.eslintrc': Cannot find module 'eslint-plugin-prefer-object-spread' ↓

cause ESLint plugin not installed

fix

Run npm install --save-dev eslint eslint-plugin-prefer-object-spread

error Parsing error: The keyword 'prefer-object-spread' is not defined ↓

cause Rule name missing plugin prefix in config

fix

Use 'prefer-object-spread/prefer-object-spread' instead of just 'prefer-object-spread'

error Configuration for rule 'prefer-object-spread/prefer-object-spread' is invalid: Severity should be one of the following: 0 = off, 1 = warn, 2 = error ↓

cause Invalid severity value in ESLint config

fix

Use numbers (0,1,2) or strings ('off','warn','error')

Warnings

gotcha The rule only flags Object.assign() when the target is an object literal. If you mutate an existing object, the rule will not flag it. ↓

fix No fix needed; this is by design. Use the rule only for cloning patterns.

gotcha Object spread only copies own enumerable properties. Object.assign() also copies own enumerable properties, but the rule assumes both are equivalent. ↓

fix Consider if you have non-enumerable properties or accessor properties. Otherwise, spread is safe.

deprecated This plugin is no longer actively maintained. ESLint's built-in 'prefer-object-spread' rule may be preferred if available. ↓

fix Migrate to ESLint's built-in 'prefer-object-spread' rule (since ESLint v5.8.0) by removing the plugin and using `"prefer-object-spread/prefer-object-spread": "error" -> "prefer-object-spread": "error"`.

Install

npm install eslint-plugin-prefer-object-spread

yarn add eslint-plugin-prefer-object-spread

pnpm add eslint-plugin-prefer-object-spread

Imports

prefer-object-spread (plugin)
wrong
```
const plugin = require('eslint-plugin-prefer-object-spread');
```
correct
```
import { rules } from 'eslint-plugin-prefer-object-spread';
```
In ESLint, plugins are typically referenced by name in config, not imported directly. When importing for testing, named exports may not exist; prefer require.
prefer-object-spread rule
wrong
```
"prefer-object-spread": "error"
```
correct
```
"prefer-object-spread/prefer-object-spread": "error"
```
Rule must be prefixed with the plugin name in ESLint config.

Plugin registration in ESLint config

wrong

{
  "plugins": ["prefer-object-spread"],
  "rules": {
    "prefer-object-spread": "error"
  }
}

correct

{
  "plugins": ["prefer-object-spread"],
  "rules": {
    "prefer-object-spread/prefer-object-spread": "error"
  }
}

ESLint rule names in config must be prefixed by the plugin name.

Quickstart

Shows how to install ESLint and the plugin, configure the rule, and see it flag Object.assign usage on an object literal.

// First install ESLint and the plugin:
// npm install --save-dev eslint eslint-plugin-prefer-object-spread

// In your .eslintrc.js:
module.exports = {
  plugins: ['prefer-object-spread'],
  rules: {
    'prefer-object-spread/prefer-object-spread': 'error'
  }
};

// Example code that would trigger the rule:
var a = Object.assign({}, foo); // Error: Use a spread property instead of Object.assign().

// Corrected version:
var a = { ...foo };