eslint-plugin-isotropic

ESLint rules for Isotropic projects with sensible defaults and consistent conventions

Installation

You'll need ESLint v9.8.0 or above:

npm install eslint --save-dev

Next, install eslint-plugin-isotropic:

npm install eslint-plugin-isotropic --save-dev

Usage

Create an eslint.config.js file in your project root directory to use the isotropic configuration:

import _eslintPluginIsotropic from 'eslint-plugin-isotropic';

export default [
    _eslintPluginIsotropic.configs.isotropic
];

Or if using CommonJS:

const _eslintPluginIsotropic = require('eslint-plugin-isotropic');

module.exports = [
    _eslintPluginIsotropic.configs.isotropic
];

Using Individual Rules

If you prefer to use only specific rules from the plugin without the entire preset:

import { defineConfig } from "eslint/config";
import _eslintPluginIsotropic from 'eslint-plugin-isotropic';

export default defineConfig([
    {
        files: ["**/*.js"],
        plugins: {
            isotropic: _eslintPluginIsotropic
        },
        rules: {
            'isotropic/prefer-date-now': 'error',
            'isotropic/prefer-reflect-apply': 'error'
            // Add other rules as needed
        }
    }
]);

Features

This plugin provides a comprehensive set of rules and configurations:

• Includes and configures several established ESLint plugins:
  • @eslint-community/eslint-plugin-eslint-comments
  • @stylistic/eslint-plugin
  • eslint-plugin-import-x
  • eslint-plugin-n
  • eslint-plugin-promise
  • eslint-plugin-regexp
• Provides sensible defaults for all ESLint core rules
• Adds several custom rules for Isotropic projects

Note: ESLint v9.x uses the new "flat config" format (eslint.config.js) instead of the deprecated .eslintrc.* configuration files. For more information, see the ESLint Configuration Files Documentation.

Custom Rules

filename-must-match-pattern

Enforces filename naming conventions through a configurable regular expression pattern.

// eslint.config.js
import { defineConfig } from "eslint/config";
import _eslintPluginIsotropic from 'eslint-plugin-isotropic';

export default defineConfig([
    {
        files: ["**/*.js"],
        plugins: {
            isotropic: _eslintPluginIsotropic
        },
        rules: {
            'isotropic/filename-must-match-pattern': ['warn', {
                pattern: '^[\\da-z](?:[\\d\\-.a-z]*?[\\da-z])?$',
                flags: 'v'
            }]
        }
    }
]);

See documentation for more details.

filename-must-not-match-pattern

Enforces that filenames do not match a specific pattern.

// eslint.config.js
import { defineConfig } from "eslint/config";
import _eslintPluginIsotropic from 'eslint-plugin-isotropic';

export default defineConfig([
    {
        files: ["**/*.js"],
        plugins: {
            isotropic: _eslintPluginIsotropic
        },
        rules: {
            'isotropic/filename-must-not-match-pattern': ['warn', {
                pattern: '^index$',
                flags: 'v'
            }]
        }
    }
]);

See documentation for more details.

prefer-date-now

Enforces using Date.now() instead of new Date().getTime() for better readability and performance.

// ❌ Incorrect
const now = new Date().getTime();

// ✅ Correct
const now = Date.now();

See documentation for more details.

prefer-reflect-apply

Encourages using Reflect.apply() over Function.prototype.apply() and Function.prototype.call().

// ❌ Incorrect
someFunction.call(object, ...args);
someFunction.apply(object, args);

// ✅ Correct
Reflect.apply(someFunction, object, args);

See documentation for more details.

sort-keys

Requires object keys to be sorted in a consistent order. This rule extends the functionality of ESLint's built-in sort-keys rule with natural sorting options.

// ❌ Incorrect
const object = {
    c: 3,
    b: 2,
    a: 1
};

// ✅ Correct
const object = {
    a: 1,
    b: 2,
    c: 3
};

Configuration example:

// eslint.config.js
import { defineConfig } from "eslint/config";
import _eslintPluginIsotropic from 'eslint-plugin-isotropic';

export default defineConfig([
    {
        files: ["**/*.js"],
        plugins: {
            isotropic: _eslintPluginIsotropic
        },
        rules: {
            'isotropic/sort-keys': ['error', {
                caseSensitive: false,
                direction: 'asc',
                ignoreSpecialCharacters: true,
                prefixPositions: { _: 'last' }
            }]
        }
    }
]);

Options:

• caseSensitive: Whether sorting should be case-sensitive (default: false)
• direction: Sort direction, either 'asc' or 'desc' (default: 'asc')
• ignoreSpecialCharacters: Whether to ignore special characters during sorting (default: true)
• prefixPositions: Define positions for prefixed keys (default: { _: 'last' })

See documentation for more details.

sort-vars

Requires variable declarations to be sorted in a consistent order. This rule extends the functionality of ESLint's built-in sort-vars rule with natural sorting and handling of multiline declarations.

// ❌ Incorrect
const c = 3,
    b = 2,
    a = 1;

const {
    c,
    b,
    a
} = object;

// ✅ Correct
const a = 1,
    b = 2,
    c = 3;

const {
    a,
    b,
    c
} = object;

Configuration example:

// eslint.config.js
import { defineConfig } from "eslint/config";
import _eslintPluginIsotropic from 'eslint-plugin-isotropic';

export default defineConfig([
    {
        files: ["**/*.js"],
        plugins: {
            isotropic: _eslintPluginIsotropic
        },
        rules: {
            'isotropic/sort-vars': ['error', {
                caseSensitive: false,
                direction: 'asc',
                ignoreSpecialCharacters: true,
                prefixPositions: {},
                strictEmptyLines: true
            }]
        }
    }
]);

Options:

• caseSensitive: Whether sorting should be case-sensitive (default: false)
• direction: Sort direction, either 'asc' or 'desc' (default: 'asc')
• ignoreSpecialCharacters: Whether to ignore special characters during sorting (default: true)
• prefixPositions: Define positions for prefixed variables (default: {})
• strictEmptyLines: Whether to enforce rules about empty lines between variables (default: true)

See documentation for more details.

top-scope-prefix

Enforces that variables in the top scope of a module use a specific prefix, helping distinguish globals from local variables.

// ❌ Incorrect
const constVariable = null;
function functionVariable() {}

// ✅ Correct
const _constVariable = null;
function _functionVariable() {}

Configuration example:

// eslint.config.js
import { defineConfig } from "eslint/config";
import _eslintPluginIsotropic from 'eslint-plugin-isotropic';

export default defineConfig([
    {
        files: ["**/*.js"],
        plugins: {
            isotropic: _eslintPluginIsotropic
        },
        rules: {
            'isotropic/top-scope-prefix': ['error', {
                prefix: '_'
            }]
        }
    }
]);

Options:

• prefix: The prefix that must be used for top-scope variables (default: '_')

See documentation for more details.

Key Linting Decisions

Consistent Code Style

The plugin enforces a consistent code style through the Stylistic plugin, including:

• Consistent indentation (4 spaces)
• No semicolon-less code
• Consistent spacing in code
• Strict single quote preference for strings
• Enforced curly braces for all blocks

Natural Sorting

For rules involving sorting (variables, object keys), the plugin uses isotropic-natural-sort which provides sensible ordering that matches human expectations.

Module Structure

The plugin encourages a clear module structure with:

• Underscore-prefixed module-level variables to distinguish them from local variables
• Consistent import ordering
• Proper module export patterns

Modern JavaScript Features

The plugin encourages use of modern JavaScript features:

• ES modules over CommonJS
• Modern APIs like Reflect.apply() and Date.now()
• Consistent use of ES6+ features

Combining with Other Configurations

You can combine the isotropic configuration with other configurations:

// eslint.config.js
import js from "@eslint/js";
import _eslintPluginIsotropic from 'eslint-plugin-isotropic';

export default [
    js.configs.recommended,
    _eslintPluginIsotropic.configs.isotropic,
    {
        files: ["**/*.js"],
        rules: {
            // Override specific rules
            "no-unused-vars": "warn"
        }
    }
];

Compatible ESLint Versions

This plugin requires ESLint 9.8.0 or later and uses ESLint's new flat config system.