Aa Case Converter

Complete Guide: Case Converter

Naming conventions are one of the most fundamental aspects of code style, and different languages, frameworks, and contexts each have strong conventions. A case converter lets you instantly transform text between any naming style — essential when mapping between systems that use different conventions, like converting database column names to JSON API keys.

The Major Naming Conventions

• camelCase — First word lowercase, subsequent words capitalized. No separators. Example: getUserProfile. Used in: JavaScript variables and functions, Java, Swift, Kotlin, JSON keys.
• PascalCase (UpperCamelCase) — Every word capitalized. No separators. Example: UserProfileService. Used in: PHP classes, C# types, TypeScript interfaces, React components.
• snake_case — All lowercase, words separated by underscores. Example: user_profile_id. Used in: Python variables and functions, Ruby, database column names, Rust variables.
• kebab-case (hyphen-case) — All lowercase, words separated by hyphens. Example: user-profile-card. Used in: CSS class names, HTML attributes, URL slugs, npm package names.
• SCREAMING_SNAKE_CASE (UPPER_SNAKE_CASE) — All uppercase, words separated by underscores. Example: MAX_RETRY_COUNT. Used in: constants in Python, Java, C/C++, environment variables, SQL.
• Title Case — First letter of each significant word capitalized. Example: The Quick Brown Fox. Used in: headings, book titles, UI labels.

When Each Convention is Used

Knowing which convention to use in which context prevents code review comments and style inconsistencies:

// JavaScript — camelCase for variables, PascalCase for classes
const userName = 'alice';
class UserProfile { }

// Python — snake_case for everything except classes
user_name = 'alice'
class UserProfile:
    pass

/* CSS — kebab-case */
.user-profile-card { color: red; }

-- SQL — UPPER_SNAKE for keywords, snake_case for identifiers
SELECT user_id, first_name FROM user_profiles WHERE is_active = TRUE;

Converting Database Column Names to API JSON Keys

A common real-world use case: your database uses snake_case column names (first_name, created_at), but your REST API returns camelCase JSON keys (firstName, createdAt). Many ORMs handle this automatically, but when they don't, you need a reliable conversion function.

Regex Patterns for Word Boundary Splitting

Programmatic case conversion relies on correctly identifying word boundaries. Different input formats require different splitting strategies:

// Split snake_case or kebab-case
const words = 'user_profile_id'.split(/[-_]+/);

// Split camelCase or PascalCase
const words2 = 'userProfileId'.split(/(?=[A-Z])/);

// Universal splitter (handles all common formats)
function toWords(str) {
  return str
    .replace(/([a-z])([A-Z])/g, '$1 $2')
    .replace(/[-_]+/g, ' ')
    .toLowerCase()
    .split(' ')
    .filter(Boolean);
}

Unicode-Aware Case Conversion Pitfalls

Standard toUpperCase() and toLowerCase() handle most Latin characters correctly, but some languages have special rules. The most famous example is Turkish: the dotted İ (capital I with dot) and dotless ı (lowercase i without dot) are separate letters. 'i'.toUpperCase() returns I in English locale but should return İ in Turkish locale:

// Use locale-aware methods for Turkish content
'istanbul'.toLocaleUpperCase('tr-TR'); // → 'İSTANBUL'
'İSTANBUL'.toLocaleLowerCase('tr-TR'); // → 'istanbul'

• Generate URL-safe slugs from any text with the Slug Generator.
• Analyze and count words in your text with the Word Counter.