Rules Reference

Complete guide to ESLint rules

ESLint Rules

ESLint rules are the core of the linter - they analyze your code and report problems. Each rule is independent and can be configured individually.

Rule Types

Rules are categorized by their purpose:

• Problem Rules: These rules identify code that will cause errors or unexpected behavior
• Suggestion Rules: These rules suggest alternate ways of doing things
• Layout Rules: These rules care about how the code looks rather than how it executes

Using Rules

Configure rules in your ESLint configuration file:

module.exports = {
  rules: {
    'semi': ['error', 'always'],
    'quotes': ['error', 'single'],
    'no-unused-vars': 'warn'
  }
};

Rule Severity

Each rule can be set to one of three severity levels:

• "off" or 0 - turn the rule off
• "warn" or 1 - turn the rule on as a warning (doesn’t affect exit code)
• "error" or 2 - turn the rule on as an error (exit code will be 1)

Browse Rules by Category

View rules organized by their purpose:

• Problem Rules - Prevent errors and bugs
• Suggestion Rules - Code improvements
• Layout Rules - Code formatting

Search Rules

Use the search below to find specific rules:

You can search by rule name, category, or keywords related to what the rule checks.

Popular Rules

Problem Detection

• array-callback-return - Enforce return statements in array callbacks
• no-await-in-loop - Disallow await inside loops
• no-constant-binary-expression - Disallow expressions that always evaluate to the same value

Best Practices

• eqeqeq - Require === and !==
• no-eval - Disallow eval()
• curly - Enforce consistent brace style

Code Style

• semi - Enforce semicolons
• quotes - Enforce quote style
• indent - Enforce consistent indentation