By now there should be very few Domino Developers who haven't, at the very least, tried using JavaScript in their applications. The extent to which people use it tends to vary hugely. There are experts out there and there are people who have reached as far as the line of code necessary to check the value of a field isn't blank.

I can't think of any other language in which the level of knowledge varies so much between users. I have been proclaimed a Guru by somebody I once helped to debug a simple few lines of code. Please, I am not a guru - just somebody who has taken the time to learn JavaScript and the Browser Document Object Model (DOM). The Notes.net Café features numerous comments like I'm trying to use this bit of code but I don't know JavaScript very well or I wrote this JavaScript but I am stuck now because I am a novice. Those that never take the language any further than its basic uses tend to be left with a lot of misconceptions about what JavaScript is and what it can and can't do. This article is not about to describe either of these in any great detail. All I will say is that JavaScript is a lot more than you are probably thinking and well worth taking time to get to know in depth.

If the above applies to you then it is probably better to carry on learning it a little more instead of reading this article.

So you know JavaScript then do you? Do you know about Regular Expressions? You may have heard of them already if you have developed in other languages such as Perl or AWK. If you haven't then you are missing out on a very powerful feature that could save you lines and lines of code and hours of effort.

What are Regular Expressions:

Basically, a Regular Expression (RegExp) is used to describe a pattern that can then be used to test the format of a string. Its main use to us as Domino Developers is in our form level data validation. We can use RegExps to easily check for certain patterns in the data and alert the user when it is badly formatted. We could probably do the same thing without RegExps but, trust me, they are a lot simpler to code.

There are a myriad of sites out there covering RegExps in more detail than this article could ever start to touch upon. For that reason I shall crack on with a few simple examples, an overview of the characters we need to know about and then discuss how we can use them in our Domino Forms. There is a list of a few of the better of the sites at the bottom.

A quick example:

Let's say we have a field in which we want to check the user has entered a sixteen digit number. How might an inexperienced developer write the validation function? Maybe something like this:

function isNumberSixteenDigitsLong( val ){
//check there is a value and it's the right size
if ( val == "" || val.length != 16 ){
return false;
}

//check each digit is a number
for ( var i = 1; i < val.length; i++ ){
if ( '0123456789'.indexOf(val.charAt( i )) == -1 ){
return false;
}
}

//everything is OK
return true;
}

This works well enough but consider the same function if we were to use a Regular Expression:

function isNumberSixteenDigitsLong( val ){
return /^\d{16}$/.test( val );
}

Hence we have a one line function rather than a nine line function. That has to be worth learning this for alone. Don't start worrying just yet about what the funny looking /^\d{16}$/ part is. All will come clear very soon.

How do I write a Regular Expression:

First thing we do is declare it as a variable. Its value is always inside the / and / limiters and followed by any of the optional parameters that we shall cover later. You can declare the variable like the two examples below or in the manner I used in the above example.

var re = /codestore/

or

var re = new RegExp('codestore', 'i')

This would be used to match the word "codestore" anywhere within a string. This is just a simple example of RegExp declaration. Not very useful in itself as we can easily use the string object's indexOf() method instead.

OK, let's get the boring bits out of the way. Firstly, Table 1. This shows us the most common of the special characters we have available to use, such as the \d (used to match numeric digits) that we used above. The special characters are placed in the pattern at the point at which you want to test for the string that they represent.

• Find all occurrences of 2 or more spaces in a string
• Pattern = /\s{2,}/g
• Match = 'R  5'
• Fails = 'R 5'

• A string that has one or more spaces at the start
• Pattern = /^\s+/
• Match = ' test' or ' test'
• Fail = 'test ' or 'test 1 '

• Any letter OR any number
• Pattern = /^([a-zA-Z]|\d)$/
• Match = 'F', 'p' or '7'
• Fail = '&', 'f1', or 'TT'

• A number with a sign in front of it
• Pattern = /^(\+|-)?\d+$/
• Match = +1 or -193
• Fail = 98 or 163-

• A string that ends in a letter
• Pattern = /[a-zA-Z]$/
• Match = 'Test' or '12E'
• Fail = 'Test1' 'Jake '

• A currency in pounds or dollars
• Pattern = /(\$|£)\d+/
• Match = '$99' or '£44'
• Fail = '99$' '140.00'

• Email address
• Pattern = /^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/
• Match = Jake.howlett@example.com
  Jake@example.com
• Fail = Jake@example.co.uk
  n@a.c

• A number in the format 99-9ZZ-9999-ZZ
• Pattern = /^\d{2}\-\d[A-Z]{2}\-\d{4}\-[A-Z]{2}$/
• Match = '13-8AB-6789-CD'
• Fail = '14-3ab-67OP-5f'

• A Pass-Thru tag
• Pattern = /(\SSB<.[^(><.)]+>)//\ESB<.+>/
• Match = 'SBHelloESB
• Fail = 'SB< This is a '

1. The expression to use in the validation (without the //)
2. The field whose value we want to validate
3. The action we want to perform (Test or Replace)
4. The value to replace any occurrence with