toUpperCase

toUpperCase is a string transformation operation that converts all alphabetic characters in a string to uppercase. It typically returns a new string and does not modify the original input. The transformation uses Unicode case mappings so that letters from various scripts are converted to their uppercase equivalents, while non-letter characters such as digits and punctuation remain unchanged.

In many programming languages, the function is exposed as a method named toUpperCase on string values. For example, in JavaScript, "hello".toUpperCase() returns "HELLO". Some languages also demonstrate common edge cases, such as "straße".toUpperCase() yielding "STRASSE" due to the German sharp s being mapped to "SS" in uppercase. It is important to note that the standard toUpperCase method is typically not locale-aware; it relies on a default Unicode mapping rather than language-specific rules.

For locale-aware casing, many environments provide a separate variant, such as toLocaleUpperCase(locale). This allows uppercase mapping to follow rules of a specified locale (for example, Turkish). Locale-specific behavior can differ from the default mapping, particularly for languages with special casing rules like Turkish and Azerbaijani, where certain letters transform in language-dependent ways.

Compatibility and usage notes: The concept appears across many languages, including Java, C#, Python, and JavaScript. Implementations vary in how fully they handle Unicode and locale-specific rules. When exact casing behavior matters (for example, in user-facing text or case-insensitive comparisons), developers may choose to use locale-aware variants or additional normalization steps.