isNumericOnlys

isNumericOnlys is a name used for a function or method in software libraries that determines whether a given string contains only numeric characters. It returns a boolean value indicating whether every character of the input string is a decimal digit. The exact definition of numeric characters, however, varies by language and library.

Most implementations restrict to ASCII digits 0 through 9, so a string like '12345' passes but '123a' or '12.3' does not. Some variants, however, may allow leading plus or minus signs, or interpret a broader set of Unicode digits, which changes the result for strings such as '１２３' (full-width digits) or '۳۲۱' (Persian digits). Because of these differences, the behavior of isNumericOnlys should be clarified in documentation for a given project or language.

Common implementations in popular languages illustrate the general approach. In Python, one might implement it as all(ch.isdigit() for ch in s). In JavaScript, a regex such as /^\d+$/ is commonly used. In Java, s.matches("\\d+"); and in PHP, ctype_digit($s) provides a similar check. Some platforms prefer explicit regular expressions, while others rely on built-in digit-checking utilities. Developers should choose based on whether ASCII-only digits or broader Unicode digits are required.

Edge cases include the empty string, which many definitions treat as false, and strings containing whitespace or formatting characters. If locale-aware or Unicode support is needed, the implementation should specify whether non-ASCII digits and decimal separators are accepted. Uses include input validation for numeric fields, form processing, and data sanitation, with careful testing and clear documentation of the exact criteria.