advanced-linting-techniques

Advanced Linting Techniques in TypeScript:

Here are key points and examples related to setting up and using ESLint with TypeScript for code linting and maintaining coding standards:

• Use ESLint over TSLint:

  // In your development environment setup, replace any usage of TSLint with ESLint.

• ESLint with TypeScript:

  // Install the necessary ESLint packages for TypeScript support:
  npm install --save-dev @typescript-eslint/parser @typescript-eslint/eslint-plugin

• Extending Configuration:

  // In your .eslintrc.json file, extend from the recommended TypeScript configurations:
  {
    "extends": [
      "eslint:recommended",
      "plugin:@typescript-eslint/eslint-recommended",
      "plugin:@typescript-eslint/recommended"
    ]
  }

• Custom Rules:

  // Customize or override rules in your .eslintrc.json file:
  {
    "rules": {
      "quotes": ["error", "double"],
      "@typescript-eslint/no-unused-vars": ["error"]
    }
  }

• Linting with Type Information:

  // Provide the path to your tsconfig.json file to enable rules that require type information:
  {
    "parserOptions": {
      "project": "./tsconfig.json"
    }
  }

• Ignore Patterns:

  // In your .eslintignore file, specify patterns for files to ignore:
  dist/
  node_modules/

• Auto-Fixing:

  // Use the --fix flag with the ESLint command to auto-fix certain issues:
  eslint . --fix

• Lint Staged Files:

  // Setup lint-staged in your package.json to lint only staged files on pre-commit:
  {
    "husky": {
      "hooks": {
        "pre-commit": "lint-staged"
      }
    },
    "lint-staged": {
      "*.ts": "eslint --fix"
    }
  }

• Integrate with Editors:

  // Install an ESLint plugin or extension in your code editor for real-time linting feedback.

• Use ESLint Plugins:

  // Install additional ESLint plugins for specific frameworks or libraries:
  npm install --save-dev eslint-plugin-react eslint-plugin-import

These steps help set up ESLint for a TypeScript project, ensuring that the code follows best practices and is consistent across the team. Integrating these tools into the development workflow can greatly improve code quality and readability.

Here are the key points with concise code examples for TypeScript:

Performance Optimization:

Using the --cache flag with ESLint to only lint files changed since the last linting improves performance. This is especially beneficial in large projects.

eslint . --cache  # Runs ESLint only on changed files

Rule Severity Levels:

Configuring ESLint rule severity levels helps manage the priority of issues. "Error" should be used for critical issues, "warn" for important but not critical issues, and "off" to disable rules.

{
  "rules": {
    "no-unused-vars": "warn",
    "eqeqeq": "error",
    "no-console": "off"
  }
}

Consistent Coding Conventions:

Enforcing coding conventions using ESLint rules ensures consistent code style. For example, you can enforce camelCase naming convention and consistent indentation.

{
  "rules": {
    "camelcase": "error",
    "indent": ["error", 2]
  }
}

Integrate Linting into Build Process:

Integrating linting into the CI process helps catch issues early. You can add an ESLint step in your CI configuration file.

# In a GitHub Actions workflow file
jobs:
  build:
    steps:
    - name: Lint Code
      run: eslint .

Stay Updated:

Keeping ESLint and its plugins updated ensures access to the latest features and bug fixes. Update dependencies regularly in your package.json.

npm update eslint @typescript-eslint/parser @typescript-eslint/eslint-plugin

Each code example corresponds to the bullet point above it, showing how to apply those concepts in a TypeScript project.