Chuyển Đổi Chữ Hoa Thường

What does this tool do

The Text Case Converter changes the case of text in two ways. Predefined mode: one-click conversion of the entire text to uppercase, lowercase, title case, sentence case, camelCase, PascalCase, snake_case, kebab-case, or CONSTANT_CASE. Regex mode: apply a case transformation (uppercase, lowercase, or title) only to text that matches a regular expression; non-matching text stays unchanged. Useful for formatting headings, converting identifiers, normalising data, or selectively transforming parts of text (e.g. uppercase acronyms only).

How to use it

Predefined mode

1. Select mode — Choose "Predefined".
2. Enter text — Paste or type the text to convert.
3. Select preset — Click a preset (UPPERCASE, lowercase, Title Case, etc.).
4. Copy result — The output updates live; copy when done.

Regex mode

1. Select mode — Choose "Regex".
2. Enter text — Paste or type the text to process.
3. Use presets or add patterns — Click a regex preset (e.g. "Lowercase words → UPPERCASE", "All words → Title case") to apply a pattern+case combination instantly, or enter one or more regex patterns manually. Each pattern is applied in order (output of rule 1 becomes input to rule 2). Use "Add pattern" to add more rules.
4. Choose case per rule — Each rule has its own case mode (uppercase, lowercase, title, camelCase, etc.).
5. Set flags — Toggle global (g), case-insensitive (i), multiline (m), dot-all (s) as needed. Flags are shared across all rules.
6. Copy result — Output updates live; invalid pattern shows an inline error under the failing rule.

How it works

Predefined mode: The input is transformed according to the selected case. Word boundaries for title and sentence case use whitespace; camelCase and snake_case split on spaces, hyphens, and underscore/camel boundaries. Regex mode: One or more regex patterns can be applied sequentially. Each rule specifies a pattern and a case mode; output of rule N becomes input to rule N+1. Patterns are validated with new RegExp() before use. If valid, each match is replaced with the same text in that rule's chosen case; everything else is unchanged. On the first validation or runtime error, the chain stops and shows the error under the failing rule. All processing runs client-side. No data is sent to any server.

Use cases & examples

• Format headings — Convert MY HEADING → My Heading (title case).
• Variable names — Convert my variable name → myVariableName (camelCase) or my_variable_name (snake_case).
• Constants — Convert api key → API_KEY.
• Selective uppercase — Pattern \b[A-Z]{2,}\b with uppercase: keep acronyms like "HTML" and "API" in caps; lower-case the rest.
• Sentence case — Capitalise only the first letter of each sentence.
• Normalise data — Convert column headers or identifiers to a standard format.

Example (Regex mode)

• Pattern \b\w+\b with title case → Capitalise every word.
• Pattern \b[A-Z]{2,}\b with uppercase → Ensure acronyms stay uppercase (no change if already uppercase).
• Pattern \d+ with lowercase → Matches digits; lowercase has no effect on digits; use to target specific segments.

Example (Multiple rules)

• Rule 1: Pattern \b[A-Z]{2,}\b with UPPERCASE → Keep acronyms like "HTML" and "API" in caps.
• Rule 2: Pattern \b[a-zA-Z]+\b with lowercase → Convert remaining words to lowercase.

Limitations & known constraints

• Pattern validated first — Invalid regex shows an error; no transformation is run.
• ReDoS — Complex patterns on very long text may be slow; avoid catastrophic backtracking.
• JavaScript regex — Uses JS regex flavour; some PCRE features may differ.
• Identifier parsing — camelCase/snake_case assumes words are separated by spaces, hyphens, or underscores; mixed styles may produce unexpected results.
• Unicode — Case conversion uses JavaScript’s built-in methods; some locales may behave differently.