Dot Case Converter
dot.case writes hello.world.example. Dot case is the notation for hierarchical keys: app.database.pool.size in a properties file, checkout.form.email.error in a translation bundle, com.example.service in a package name. The dot reads as "inside", which is why configuration systems from Spring to i18next converged on it independently.
Conversions
| Input | dot.case |
|---|---|
hello world example | hello.world.example |
XMLHttpRequest | xml.http.request |
user_first_name | user.first.name |
Total Order Count | total.order.count |
XMLHttpRequest becomes xml.http.request. Each segment is treated as a level in a hierarchy rather than as a word in a name.The Same Text in Other Cases
| Case | Result |
|---|---|
| camelCase | helloWorldExample |
| PascalCase | HelloWorldExample |
| snake_case | hello_world_example |
| SCREAMING_SNAKE_CASE | HELLO_WORLD_EXAMPLE |
| kebab-case | hello-world-example |
| Train-Case | Hello-World-Example |
Where dot.case Fits
dot.case expresses hierarchy: Java and Python package names, Spring and .NET configuration keys, i18n message paths, and metric names in StatsD and Prometheus exporters. It is chosen wherever the reader should understand one segment as living inside the previous one.
Converting in Code
``javascript
const dot = (s) => words(s).map((w) => w.toLowerCase()).join('.');
`
A dot is a property accessor almost everywhere, so a dot.case key placed unquoted into JavaScript or a template silently becomes a nested lookup. Configuration libraries that flatten a.b.c into nested objects rely on exactly that ambiguity.
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
``