Validating input in perl
It excludes Mexico and the Central American nations.So far, the regular expression matches any 10-digit number.Patterns are defined using string literal characters and metacharacters.For example, the following regular expression determines whether a string contains a valid 5-digit US postal code (for sake or simplicity, other possibilities are not considered): Translated to English, this pattern states: "Starting at the beginning of the string there must be nothing other than 5 digits.Letters, numbers, and underscore are all considered word characters (see Recipe 2.6).
⋯ # [Match the remaining digits and separator.] $ # Assert position at the end of the string..
So how are regular expressions implemented in Java Script? 2) When you need to dynamically construct the regular expression, via the The Reg Exp() method allows you to dynamically construct the search pattern as a string, and is useful when the pattern is not known ahead of time.
To use regular expressions to validate a string you need to define a pattern string that represents the search criteria, then use a relevant string method to denote the action (ie: search, replace etc).
This regular expression matches three groups of digits. ( # Capture the enclosed match to backreference 1... is another character class, one that allows any one of three separators.
The first group can optionally be enclosed with parentheses, and the first two groups can optionally be followed with a choice of three separators (a hyphen, dot, or space). It’s important that the hyphen appears first in this character class, because if it appeared between other characters, it would create a range, as with .