isNumeric(): test numeric input

isNumeric(x) reports whether x is a numeric value. It is a first validation step when a calculation may receive text, empty data, or another type.

Use precise validation

Numeric is broader than the domain required by many formulas. Follow it with isFinite() to reject infinity, isInteger() for counts, or isPositive() for positive-only inputs.

Practical workflow

Validate before calling sqrt(), log(), or division. Each has additional domain rules, so a true isNumeric result alone is not sufficient.