Code Quality & Review

Learn essential practices for maintaining high code quality through reviews, automated tools, and documentation.

Code Review Process

Code reviews are systematic examinations of code changes before they're merged into the main branch.

Benefits

• Bug prevention - Catch issues before production
• Knowledge sharing - Team learns from each other
• Code consistency - Maintain style and standards
• Mentoring - Help junior developers improve

Review Checklist

• [ ] Does the code solve the intended problem?
• [ ] Is the code readable and well-documented?
• [ ] Are there any obvious bugs or edge cases?
• [ ] Does it follow team coding standards?
• [ ] Are tests included and comprehensive?
• [ ] Is the performance acceptable?

Linting and Formatting

Automated tools that enforce code style and catch common issues.

ESLint (JavaScript/TypeScript)

json
{
  "extends": ["@typescript-eslint/recommended"],
  "rules": {
    "no-unused-vars": "error",
    "prefer-const": "error",
    "no-console": "warn"
  }
}

Prettier (Code Formatting)

json
{
  "semi": true,
  "trailingComma": "es5",
  "singleQuote": true,
  "printWidth": 80
}

Benefits

• Consistency - Same style across the codebase
• Automation - No manual style discussions
• Error prevention - Catch syntax errors early

Documentation Standards

Good documentation makes code maintainable and helps team collaboration.

Code Comments

javascript
/**
 * Calculates the total price including tax
 * @param {number} subtotal - The base price before tax
 * @param {number} taxRate - Tax rate as decimal (0.08 for 8%)
 * @returns {number} Total price including tax
 */
function calculateTotal(subtotal, taxRate) {
  return subtotal * (1 + taxRate);
}

README Structure

markdown
# Project Name
Brief description of what the project does

## Installation
Step-by-step installation instructions

## Usage
Basic usage examples

## API Documentation
Link to detailed API docs

## Contributing
Guidelines for contributors

Refactoring Techniques

Improving code structure without changing functionality.

Common Refactoring Patterns

• Extract Function - Break large functions into smaller ones
• Rename Variables - Use descriptive names
• Remove Duplication - DRY (Don't Repeat Yourself)
• Simplify Conditionals - Reduce nested if statements

Example Refactoring

javascript
// Before
function processUser(user) {
  if (user.age >= 18 && user.verified && user.active) {
    // complex logic here
  }
}

// After
function canUserAccessFeature(user) {
  return user.age >= 18 && user.verified && user.active;
}

function processUser(user) {
  if (canUserAccessFeature(user)) {
    // complex logic here
  }
}

Code Quality Metrics

Test Coverage

Percentage of code covered by tests

bash
# Generate coverage report
npm run test:coverage

Code Complexity

Cyclomatic complexity measures code paths

• Low complexity (1-10): Easy to test and maintain
• Medium complexity (11-20): More complex but manageable
• High complexity (21+): Consider refactoring

Technical Debt

Accumulated shortcuts and suboptimal solutions

• Track debt in code comments or issues
• Regularly schedule refactoring time
• Address debt before it becomes unmanageable

Tools and Setup

Pre-commit Hooks

json
{
  "husky": {
    "hooks": {
      "pre-commit": "lint-staged"
    }
  },
  "lint-staged": {
    "*.{js,ts}": ["eslint --fix", "prettier --write"]
  }
}

CI/CD Integration

yaml
- name: Lint code
  run: npm run lint

- name: Check formatting
  run: npm run format:check

- name: Run tests with coverage
  run: npm run test:coverage

Best Practices

Automate what you can - Use tools for consistency

Review everything - No code goes to production unreviewed

Keep it simple - Prefer readable code over clever code

Document decisions - Explain why, not just what

Refactor regularly - Don't let technical debt accumulate