In JavaScript numbers can be validated to be of a certain length. For example, the following regular expression can be used to validate that a numeric value is two digits in length:
document.write(/^\d\d$/.test(22));
This simply calls the \d character class twice. Using curly braces {} this statement can be made even simpler:
document.write(/^\{2}$/.test(22));
The curly braces specify that exactly the number of occurrences specified should be matched. The curly braces can be further expanded to include a comma to specify that the number of digits must match between the length specified in the first and second arguments.
document.write(/^\d{2,4}$/.test(22));
The preceding will match any digit that is between two and four digits in length.
Related articles:
JavaScript Regular Expressions
JavaScript Regular Expression Special Characters: $ ^
JavaScript Number Validation (Integer)
JavaScript Regular Expression Backslash
