String: Contains only numbers
Checks that a string contains only numbers.
Checks that a string contains only numbers. A value passes when every character is a digit from 0 to 9, with nothing else in between. Use this to confirm that a value is a plain run of digits before you treat it as one, for example a postal code, an article number, or a barcode. A decimal point, a minus sign, a space, or any letter makes the value fail, and an empty value does not match because it has no digits at all.