PascalCase Converter
PascalCase writes HelloWorldExample. It is the convention for type and class names in almost every language, for C# methods, and for React component names — where a lowercase first letter would make JSX treat the component as an HTML tag.
Conversions
| Input | PascalCase |
|---|---|
hello world example | HelloWorldExample |
XMLHttpRequest | XmlHttpRequest |
user_first_name | UserFirstName |
Total Order Count | TotalOrderCount |
XMLHttpRequest stays intact in PascalCase, but Go's own style guide requires initialisms to be fully capitalised — ServeHTTP, not ServeHttp — while C# convention capitalises only the first letter of an acronym longer than two characters.The Same Text in Other Cases
| Case | Result |
|---|---|
| camelCase | helloWorldExample |
| snake_case | hello_world_example |
| SCREAMING_SNAKE_CASE | HELLO_WORLD_EXAMPLE |
| kebab-case | hello-world-example |
| Train-Case | Hello-World-Example |
| dot.case | hello.world.example |
Where PascalCase Fits
PascalCase names things rather than values: classes, types, interfaces, enums, React components and exported Go identifiers. In several languages that distinction is enforced rather than advised, which makes the case a semantic marker instead of a style preference.
Converting in Code
``javascript
const pascal = (s) =>
words(s)
.map((w) => w[0].toUpperCase() + w.slice(1).toLowerCase())
.join('');
`
Lower-casing the remainder of each word destroys deliberate internal capitals. parseJSON becomes ParseJson, which is correct C# and wrong Go — the convention has to be a parameter, not a hard-coded rule.
Converting at the API Boundary
The recurring friction is that JavaScript uses camelCase and Python, Ruby, Go and SQL use
snake_case. The fix is to convert in exactly one place — the client that talks to the API —
rather than letting both conventions into the same codebase.
`javascript
const toCamel = (s) => s.replace(/_([a-z])/g, (_, c) => c.toUpperCase());
const toSnake = (s) => s.replace(/[A-Z]/g, (c) => '_' + c.toLowerCase());
// Recursively, for a whole payload
const convertKeys = (value, fn) =>
Array.isArray(value)
? value.map((v) => convertKeys(v, fn))
: value && typeof value === 'object'
? Object.fromEntries(Object.entries(value).map(([k, v]) => [fn(k), convertKeys(v, fn)]))
: value;
`
Two things to watch: keys that are user data rather than field names must not be
converted, and the round trip is not always lossless — userID → user_id → userId
changes the original.
Where Each Convention Is Mandatory
Not stylistic — these will break if you deviate:
| Context | Requirement |
|---|---|
| Environment variables | Uppercase with underscores; POSIX reserves lowercase |
| Custom HTML elements | Must contain a hyphen |
| Python modules | Cannot contain hyphens; the import statement will not parse |
| SQL identifiers | Folded to one case unless quoted, so camelCase does not survive |
| React components | Must start uppercase, or JSX treats it as an HTML tag |
Renaming Safely
A find-and-replace across a codebase will hit strings, comments and unrelated identifiers.
Use your language server's rename symbol instead — it understands scope. For a bulk rename
across files, restrict the pattern with word boundaries and review the diff before
committing:
`bash
grep -rn '\buserId\b' src/ # look first
``