Validating a date in javascript

11 May

The regexes in these recipes are all pretty straightforward, but hopefully this gives an example of the depth you can expect from the book. Both are followed by a question mark, which makes them optional.For more than 100 detailed regular expression recipes that include equal coverage for eight programming languages (C#, Java, Java Script, Perl, PHP, Python, Ruby, and VB. We’ll explain more about the question mark after discussing the other types of tokens in this regular expression.The following layout breaks the regular expression into its individual parts, omitting the redundant groups of digits: ^ # Assert position at the beginning of the string. Any quantifier that allows something to be repeated zero times effectively makes that element optional.Using a library to do form validation can save lots of your development time. j Query Form validation library is the most popular validation library.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 .

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If it is, it then gets each date part and then tests that it is actually a real date.NET), get your very own copy of , so that your phone number records are consistent. The parentheses that appear without backslashes are capturing groups and are used to remember the values matched within them so that the matched text can be recalled later.A regular expression can easily check whether a user entered something that looks like a valid phone number. In this case, backreferences to the captured values are used in the replacement text so we can easily reformat the phone number as needed.By using capturing groups to remember each set of digits, the same regular expression can be used to replace the subject text with precisely the format you want. Two other types of tokens used in this regular expression are character classes and quantifiers.See Recipes 3.5 and 3.15 for help implementing this regular expression with other programming languages. Character classes allow you to match any one out of a set of characters.