IsNumeric

IsNumeric is a predicate or function used in programming to determine whether a value can be interpreted as a numeric value. The exact rules vary by language and library, but the goal is to distinguish numbers (such as integers and floating-point values) from non-numeric data. In practice, isNumeric is commonly used for input validation, parsing, and data normalization.

In PHP, the is_numeric function returns true if the argument is a number or a numeric string. This includes integers, floats, and strings that represent numbers, including scientific notation. It returns false for non-numeric strings and for values that are not numeric in nature.

In JavaScript, there is no built-in universal isNumeric function. Developers typically implement a check by attempting to convert the value to a number and testing for finiteness, for example by using Number(value) and isFinite. Such checks generally return true for numeric strings like "42" or "-3.14" and false for empty strings or strings containing non-numeric characters.

In Python, numeric testing uses different approaches: numeric types (int, float, complex) are inherently numeric, while strings may be tested with conversion attempts (for example, attempting float(s) inside a try/except block) or with methods like isnumeric, isnumeric, or isdecimal, which have distinct semantics and may not cover all numeric representations.

Caution isNumeric implementations often differ in handling whitespace, signs, decimal points, exponent notation, locale rules, and Unicode digits. Depending on the context, it may be safer to perform explicit parsing or type conversion rather than rely on a single isNumeric check.