According to Goyvaerts and Levithan in their book, Regular Expressions Cookbook, “Regular expression is a specific kind of text pattern that you can use with many modern applications and programming languages.”
We can use regular expression to verify many things in our applications, such as credit card numbers, email addresses, social security numbers, zip codes, dates, etc.
I was assigned to create a web-page that calculated employees’ ages by filling out the date of birth employees. As we know, date has its own pattern that we cannot violate it in our application. If someone input the date incorrectly, it will damage our data in database. Therefore, we have to verify all data before insert it in to the database.
Figure 1: Date is typed incorrectly
Figure 1 shows us a message box that appears after someone typing a wrong date pattern. We know that there is 12 months in a year and 30 days in even months, and 31 days in odd months.
Figure 2: Regular expression pattern
Figure 2 shows us the regular expression pattern that I used to verify the date. However, the pattern did not cover the date of February in the Leap Year. So, I created a little bit javascript code to cover that issue. Please see Figure 3.
Figure 3: Javascript code for leap year
So, if someone type 02-29-1987, the message box will pop up like in the Figure 4.
Figure 4: February 1987
If someone type 02-29-1988, which is a correct date pattern, the application will calculate the ages automatically. Please see figure 5.
Figure 5: Ages has been calculated
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