startsWith

startsWith is a string operation that tests whether a string begins with a specified prefix. It returns a boolean value: true if the string starts with the prefix, false otherwise. The basic idea is consistent across languages, though exact syntax and edge cases differ. Most implementations are case-sensitive by default, and an empty prefix typically yields true for any string.

In JavaScript, the method String.prototype.startsWith(searchString, position) returns true if the string begins with searchString at or after the optional position index. If position is omitted, it defaults to 0.

In Python, str.startswith(prefix, start, end) returns True if the slice of the string from start to end begins with prefix. The prefix can be a single string or a tuple of prefixes.

In Java and C#, similar functionality is provided by startsWith, with language- and overload-specific details. Java's String.startsWith(String prefix, int toffset) and C# String.StartsWith(string value) are typically case-sensitive unless a different comparer is used.

PHP 8 adds str_starts_with(string, prefix) as a dedicated boolean check. Older PHP code often used substr or strpos comparisons instead.

C++20 introduces std::string::starts_with as a standard member function.

Examples: "Hello world".startsWith("Hello") evaluates to true in languages that support the method; Python: "apple pie".startswith("apple") is true; PHP: str_starts_with("abcdef", "abc") is true.

Uses include input validation, path and URL prefix checks, and normalization when case-insensitive comparisons are required.