Pro PHP and jQuery by Jason Lengstorf.pdf - Computer Science ...

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CHAPTER 9 ■ PERFORMING FORM VALIDATION WITH REGULAR EXPRESSIONS
Figure 9-23. The error message displayed when invalid dates are supplied
Adding Client-Side Date Validation
For most users, JavaScript will be enabled. It’s far more convenient as a user to get instant feedback on
the form, so you will add new jQuery functionality to validate date strings on the client side.
Creating a New JavaScript File to Validate the Date String
Because you’re going to continue to work with this script in the next chapter, you should put it in a
separate file in the js folder called valid-date.js. This file will contain a function that is functionally
equivalent to the _validDate() method in the Calendar class.
It will accept a date to validate, check it against the date-matching regex pattern you wrote
previously using match(), and then return true if a match is found or false if match() returns null.
You build this function by inserting the following code into valid-date.js:
// Checks for a valid date string (YYYY-MM-DD HH:MM:SS)
function validDate(date)
{
// Define the regex pattern to validate the format
var pattern = /^(\d{4}(-\d{2}){2} (\d{2})(:\d{2}){2})$/;
}
// Returns true if the date matches, false if it doesn't
return date.match(pattern)!=null;
■ Note The regex pattern is not enclosed in quotes. If you used quotes, the pattern would be stored as a string
and interpreted accordingly—this would result in the script looking for an exact character match, rather than
interpreting the regex pattern properly.