hasPrefix

hasPrefix is a common programming construct used to determine whether a string begins with a specified prefix. It is frequently employed to route logic, validate input formats, or identify data categories based on initial characters.

In languages that expose a string method named hasPrefix (notably Swift), hasPrefix takes a prefix argument and returns a boolean indicating whether the string starts with that prefix. The check is typically case-sensitive, following the language’s standard string comparison rules. If the string starts with the given prefix, the result is true; otherwise, it is false. Example: let s = "https://example.com"; if s.hasPrefix("https://") { /* handle secure URL */ }

hasPrefix is often contrasted with similar approaches such as hasSuffix (which checks the end of a string) or with generic substring search functions. In many ecosystems, the concept is available under different names, such as startsWith or beginsWith, but the underlying goal remains the same: a fast test for a leading sequence of characters.

Performance characteristics generally depend on the implementation and the length of the prefix, with the operation examining up to the length of the prefix. Edge cases are typically straightforward: an exact match at the start yields true, while a mismatch yields false. For case-insensitive checks, developers usually normalize case or use a language-specific alternative that supports case-insensitive comparison.

Related topics include string comparison semantics, localization considerations for Unicode text, and alternative methods for prefix matching in other languages.