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Regular Expressions

and VBScript

Regular expressions were introduced to VBScript in version 5.0. They can be used to parse character sequences (strings) and can be used to provide flexible replace functionality.

VBScript can be used on the client side in Web pages when the Internet Explorer browser provides the VBScript interpreter or in the Windows Script Host (WSH).

The VBScript interpreter (vbscript.dll) does not allow file access, but the associated file, scrrun.dll, allows VBScript when used with WSH, for example, to have file access and allows directory manipulation.

In this chapter, you will learn the following:

How to use the properties and methods of the RegExp object

How to use the Match object and the Matches collection

The metacharacters supported in VBScript and how to use them

How to use VBScript regular expressions to solve some text-handling problems

The RegExp Object and How to Use It

The RegExp object, the Match object, and the Matches collection all relate to how regular expressions are used in VBScript. This section focuses on the RegExp object.

The RegExp object has three properties and three methods. The properties are as follows:

Pattern property

Global property

IgnoreCase property

Chapter 20

Each of these properties is described in the following sections. The three methods are as follows:

Execute method

Replace method

Test method

Each of these methods is described and demonstrated in the following sections. To carry out simple matching, the Pattern property and the Test() method are often used.

The RegExp Object’s Pattern Property

The VBScript RegExp object differs in functionality from the tools and languages discussed earlier in this book. For example, there is no syntax in VBScript like the following JScript declaration and assignment statement:

var myRegExp = /\d{3}/;

Instead, VBScript uses the value of the RegExp object’s Pattern property to hold a string value, which is the regular expression pattern.

So the VBScript equivalent of the preceding JScript code would look like this:

Dim myRegExp

Set myRegExp = new RegExp myRegExp.Pattern = “\d{3}”

The following example shows a very simple function that uses the Pattern property as part of a simple replace operation.

Try It Out

A Simple Match Operation

The sample file, TestForA.html, shows how the Pattern property is used:

<html>

<head>

<title>Test For Upper Case A</title>

Dim myRegExp, TestString Set myRegExp = new RegExp myRegExp.Pattern = “A”

TestString = “Andrew”

If myRegExp.Test(TestString) = True Then

MsgBox “The test string ‘“ & TestString & “‘ matches the pattern ‘“ & myRegExp.Pattern & “‘.”

Else

MsgBox “There is no match.” End If

End Function

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Regular Expressions and VBScript

</script>

</head>

</body>

</html>

Open TestForA.html in Internet Explorer, and notice the message box that is displayed when the page loads.

Figure 20-1 shows the appearance of the message box that is displayed. It correctly indicates that there is a match for the pattern A in the character sequence Andrew.

Figure 20-1

How It Works

When the HTML page loads, the MatchTest() function is called:

The functionality is all contained in the MatchTest() function:

Function MatchTest

First, the variables myRegExp (which contains the regular expression pattern in its Pattern property) and the TestString (which is supplied literally) are dimensioned:

Dim myRegExp, TestString

Next, in a Set statement, a reference to a new RegExp object is assigned to the variable myRegExp:

Set myRegExp = new RegExp

Next, a single literal character, A, is assigned to the myRegExp object’s Pattern property:

myRegExp.Pattern = “A”

Then the character sequence Andrew is assigned to the variable TestString:

TestString = “Andrew”

An If statement is used to display a message box when matching is successful. Notice that the Test() method of the myRegExp variable is used in the logical test of the If statement. The Test() method

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tests whether or not the string, which is the method’s single argument, contains a match for the value of the Pattern property of the same RegExp object, in this case, the RegExp object referenced by the myRegExp variable:

If myRegExp.Test(TestString) = True Then

The message to be displayed is constructed by concatenating literal text with the values of the TestString variable and the value of the myRegExp.Pattern property:

MsgBox “The test string ‘“ & TestString & “‘ matches the pattern ‘“ &

myRegExp.Pattern & “‘.”

An Else clause is also provided with an alternate message indicating that there is no match. However, with the supplied values for myRegExp.Pattern and TestString, the Else clause is never needed in this example. In later examples, where the test string is supplied by the user, you will need an Else clause to be in place:

Else

MsgBox “There is no match.”

Finally, the End If and End Function statements complete the MatchTest function:

End If

End Function

The RegExp Object’s Global Property

The RegExp object’s Global property can have the Boolean values True or False. The Global property’s default value is False, which means that only a single match for the value of the Pattern property is sought. When the value of the Global property is True, matching continues to be attempted throughout the test string, and multiple matches may be returned.

Try It Out

The Global Property

The test file for this example, MatchGlobal.html, is shown here:

<html>

<head>

<title>Carry out a non-global replace and a global replace.</title> <script language=”vbscript” type=”text/vbscript”>

Dim myRegExp, InputString, ChangedString

Function MatchGlobal

Set myRegExp = new RegExp myRegExp.Pattern = “A” DoReplaceDefault DoReplaceGlobal

End Function

Function DoReplaceDefault

InputString = InputBox(“Enter a string. It will be tested once to see if it contains” &VBCrLf & “any ‘A’ characters. Any ‘A’ will be replaced by ‘B’”) myRegExp.Global = False

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Regular Expressions and VBScript

ChangedString = myRegExp.Replace(InputString, “B”) If myRegExp.Test(InputString) = True Then

MsgBox “The test string ‘“ & InputString & “‘ matches the pattern ‘“ & myRegExp.Pattern & “‘.” _& VBCrLf

&“The changed string is “ & ChangedString

Else

MsgBox “There is no match. ‘“ & InputString & “‘ does not match “ &VBCrLf _

&“the pattern ‘“ & myRegExp.Pattern & “‘.”

End If

End Function

Function DoReplaceGlobal

InputString = InputBox(“Enter a string. It will be tested to see if it contains” &VBCrLf & “any ‘A’ characters. Any ‘A’ will be replaced by ‘B’”) myRegExp.Global = True

ChangedString = myRegExp.Replace(InputString, “B”) If myRegExp.Test(InputString) = True Then

MsgBox “The test string ‘“ & InputString & “‘ matches the pattern ‘“ & myRegExp.Pattern & “‘.” & VBCrLf _

&“The changed string is “ & ChangedString

Else

MsgBox “There is no match. ‘“ & InputString & “‘ does not match “ &VBCrLf _

&“the pattern ‘“ & myRegExp.Pattern & “‘.”

End If

End Function

</script>

</head>

</body>

</html>

As well as using the Global property, the code makes use of the RegExp object’s Replace() method.

When MatchGlobal.html is opened, two message boxes will be displayed. The first attempts only a single match, and the second matches as many times as there are matches in the test string.

1.Open MatchGlobal.html in Internet Explorer.

2.In the message box that appears, enter the character sequence THE APPLE IS A TASTY FRUIT. Because matching in VBScript is, by default, case sensitive, be sure to use all uppercase characters.

3.Click the OK button, and inspect the message box that is displayed.

Figure 20-2 shows the screen’s appearance after Step 3. Notice that only a single occurrence of uppercase A has been replaced.

Figure 20-2

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4.Click the OK button in the message box, and reenter the same string, THE APPLE IS A TASTY FRUIT, in the input box.

5.Click the OK button, and inspect the result displayed in the message box.

Figure 20-3 shows the screen’s appearance after Step 5. Notice that each occurrence of uppercase A has been replaced with uppercase B.

Figure 20-3

How It Works

The code in this example is split into three functions, MatchGlobal, DoReplaceDefault, and

DoReplaceGlobal.

Because the myRegExp variable is used in multiple functions, it, together with other variables, is declared globally:

Dim myRegExp, InputString, ChangedString

The MatchGlobal function uses the Set statement to create a reference, stored in the myRegExp variable, to a new RegExp object:

Function MatchGlobal

Set myRegExp = new RegExp myRegExp.Pattern = “A” DoReplaceDefault DoReplaceGlobal

End Function

Assigning the string value A to be the value of the Pattern property of myRegExp makes it the simple literal pattern that is to be matched.

The following DoReplaceDefault function accepts a string typed by the user into an input box:

Function DoReplaceDefault

InputString = InputBox(“Enter a string. It will be tested once to see if it contains” &VBCrLf & “any ‘A’ characters. Any ‘A’ will be replaced by ‘B’”) myRegExp.Global = False

ChangedString = myRegExp.Replace(InputString, “B”) If myRegExp.Test(InputString) = True Then

MsgBox “The test string ‘“ & InputString & “‘ matches the pattern ‘“ & myRegExp.Pattern & “‘.” _& VBCrLf

& “The changed string is “ & ChangedString

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Regular Expressions and VBScript

Else

MsgBox “There is no match. ‘“ & InputString & “‘ does not match “ &VBCrLf _ & “the pattern ‘“ & myRegExp.Pattern & “‘.”

End If

End Function

The input box is displayed using the VBScript InputBox() function. Notice that the information given to the user states that the string will be tested for a match only once.

To carry out the replacement of any (first) occurrence of A in the string that the user enters into the input box, the RegExp object’s Replace() method is used:

ChangedString = myRegExp.Replace(InputString, “B”)

Notice that it isn’t necessary to express the pattern to match as an argument to the Replace() method. That pattern was defined earlier when a pattern was assigned to myRegExp’s Pattern property:

myRegExp.Pattern = “A”

The two arguments to the Replace() method are, respectively, the string in which the replace operation is to be carried out (in this case, the value of the InputString variable) and the character sequence to be used to replace the first occurrence of text that matches the value of the Pattern property (in this case, the character A, which is the value of the Pattern property, is replaced by the character B, the second argument to the Replace() method).

The first occurrence of A in THE APPLE IS A TASTY FRUIT is the initial character of APPLE. That A is replaced by the second argument of the Replace() method, B. So the value of the following ChangedString variable is THE BPPLE IS A TASTY FRUIT, with the only change being the creation of the character sequence BPPLE in place of the character sequence APPLE:

ChangedString = myRegExp.Replace(InputString, “B”)

This is the default behavior, to match, and in this case, replace once.

The following DoReplaceGlobal function does almost the same thing, except that matching is attempted on the input string an unlimited number of times:

Function DoReplaceGlobal

InputString = InputBox(“Enter a string. It will be tested to see if it contains” &VBCrLf & “any ‘A’ characters. Any ‘A’ will be replaced by ‘B’”) myRegExp.Global = True

ChangedString = myRegExp.Replace(InputString, “B”) If myRegExp.Test(InputString) = True Then

MsgBox “The test string ‘“ & InputString & “‘ matches the pattern ‘“ &

myRegExp.Pattern & “‘.” & VBCrLf _

&“The changed string is “ & ChangedString

Else

MsgBox “There is no match. ‘“ & InputString & “‘ does not match “ &VBCrLf _

&“the pattern ‘“ & myRegExp.Pattern & “‘.”

End If

End Function

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This change in processing behavior occurs because the value of the Global property of the RegExp object has been set to True:

myRegExp.Global = True

Each time the value of the Pattern property, in this example, the uppercase character A, is matched, it is replaced in the variable ChangedString by the uppercase character B:

ChangedString = myRegExp.Replace(InputString, “B”)

Thus, each A in the input string THE APPLE IS A TASTY FRUIT is replaced by B, giving the value of the ChangedString variable as THE BPPLE IS B TBSTY FRUIT.

The RegExp Object’s IgnoreCase Property

The RegExp object’s IgnoreCase property allows case-insensitive matching to be carried out.

The preceding MatchGlobal.html example used an input string that was all uppercase. More naturally, instead of THE APPLE IS A TASTY FRUIT, you might input the string The apple is a tasty fruit..

The following sample file, CaseReplace.html, allows you to try out case-sensitive (the default) and case-insensitive replacement:

<html>

<head>

<title>Carry out a case-sensitive replace and a case-insensitive replace.</title> <script language=”vbscript” type=”text/vbscript”>

Dim myRegExp, InputString, ChangedString

Function MatchCaseOptions Set myRegExp = new RegExp myRegExp.Pattern = “A” myRegExp.Global = True DoReplaceSensitive DoReplaceInsensitive

End Function

Function DoReplaceSensitive

InputString = InputBox(“Enter a string. It will be tested once to see if it contains” &VBCrLf & “any ‘A’ characters. Any ‘A’ will be replaced by ‘B’”) ChangedString = myRegExp.Replace(InputString, “B”)

If myRegExp.Test(InputString) = True Then

MsgBox “The test string ‘“ & InputString & “‘ matches the pattern ‘“ & myRegExp.Pattern & “‘.” & VBCrLf _

&“The changed string is “ & ChangedString

Else

MsgBox “There is no match. ‘“ & InputString & “‘ does not match “ &VBCrLf _

&“the pattern ‘“ & myRegExp.Pattern & “‘.”

End If

End Function

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Function DoReplaceInsensitive myRegExp.IgnoreCase = True

InputString = InputBox(“Enter a string. It will be tested to see if it contains” &VBCrLf & “any ‘A’ characters. Any ‘A’ will be replaced by ‘B’”)

ChangedString = myRegExp.Replace(InputString, “B”) If myRegExp.Test(InputString) = True Then

MsgBox “The test string ‘“ & InputString & “‘ matches the pattern ‘“ & myRegExp.Pattern & “‘.” & VBCrLf _

&“The changed string is “ & ChangedString

Else

MsgBox “There is no match. ‘“ & InputString & “‘ does not match “ &VBCrLf _

&“the pattern ‘“ & myRegExp.Pattern & “‘.”

End If

End Function

</script>

</head>

</body>

</html>

Try It Out

Using the IgnoreCase Property of the RegExp Object

First, attempt to match an input string using the default value of the IgnoreCase property.

1.Open CaseReplace.html in Internet Explorer, and in the displayed input box, enter the test string The apple is a tasty fruit..

2.Click the OK button, and inspect the information displayed in the message box., as shown in Figure 20-4. Notice that there is no match at this point.

Figure 20-4

Next, attempt to match an input string with the value of the IgnoreCase property set to True. In other words, matching will be case insensitive.

3.Click the OK button to dismiss the message box that was displayed in Figure 20-4.

4.In the displayed input box, enter the test string The apple is a tasty fruit..

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5.Click the OK button, and inspect the information displayed in the message box, as shown in Figure 20-5.

Figure 20-5

How It Works

When CaseReplace.html is loaded, the function MatchCaseOptions is called:

Notice that in MatchCaseOptions, the value of the Global property is set to True, so all matches will be replaced:

Function MatchCaseOptions Set myRegExp = new RegExp myRegExp.Pattern = “A” myRegExp.Global = True DoReplaceSensitive

DoReplaceInsensitive

End Function

The DoReplaceSensitive function does a global attempted match similar to the one you saw in the preceding example.

The DoReplaceInsensitive function does a global attempted match but does it case insensitively because the value of the IgnoreCase property is set to True:

Function DoReplaceInsensitive

myRegExp.IgnoreCase = True

Every occurrence of the character A (whether lowercase or uppercase) in the input string The apple is a tasty fruit. is replaced by uppercase B, as you saw in Figure 20-5.

The RegExp Object’s Test() Method

The Test() method executes an attempted regular expression match against a specified test string and returns a Boolean value. The Boolean value returned by the Test() method can be used in a logical test. For example, you saw in an earlier example the following code, which tested whether the test string held in the TestString variable matched the value of the Pattern property and, depending on the Boolean value returned, would display a message box indicating a successful match or a failure to match.

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Regular Expressions and VBScript

If myRegExp.Test(TestString) = True Then

MsgBox “The test string ‘“ & TestString & “‘ matches the pattern ‘“ & myRegExp.Pattern & “‘.”

Else

MsgBox “There is no match.”

End If

The RegExp Object’s Replace() Method

The Replace() method replaces the part of a string that matches the pattern held in the Pattern property of the RegExp object with another string. The string in which replacement is to take place is the first argument to the Replace() method, and the replacement string is the second argument to the

Replace() method.

The Replace() method, when used together with grouping parentheses, can be used to reverse the order of parts of the string in the first argument to the method. The groups captured in the matching string can be used in reverse order in the replacement string.

Try It Out

Using the Replace() Method to Reverse Order

The test file, ReverseName.html, is shown here:

<html>

<head>

<title>Reverse Surname and First Name</title> <script language=”vbscript” type=”text/vbscript”> Function ReverseName

Dim myRegExp, TestName, Match Set myRegExp = new RegExp

myRegExp.Pattern = “(\S+)(\s+)(\S+)”

TestString = InputBox(“Enter your name below, in the form” & VBCrLf & _

“first name, then a space then last name.” & VBCrLf & “Don’t enter an initial or middle name.”)

Match = myRegexp.Replace(TestString, “$3,$2$1”) If Match <> “” Then

MsgBox “Your name in last name, first name format is:” & VBCrLf & Match Else

MsgBox “You didn’t enter your name.” & VBCrLF & “Press OK then F5 to run the example again.”

End If

End Function

</script>

</head>

</body>

</html>

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1.Open ReverseName.html in Internet Explorer.

2.In the input box that is displayed, enter your name in first name–last name format, with the first and last names separated by at least one space character.

Figure 20-6 shows the name John Smith input in the desired format.

Figure 20-6

3.Click the OK button, and inspect the results, as shown in Figure 20-7.

If a name has been entered in the requested format, firstname lastname, the name is displayed in a message box in the format lastname, firstname.

Figure 20-7

How It Works

When the Web page loads, the ReverseName function is called:

The pattern (\S+)(\s+)(\S+) is assigned to the myRegExp variable’s Pattern property:

myRegExp.Pattern = “(\S+)(\s+)(\S+)”

The preceding pattern captures three groups. The first, specified by (\S+), matches and captures one or more nonwhitespace characters. The second, specified by (\s+), matches and captures one or more whitespace characters. The third, specified by (\S+), matches and captures one or more nonwhitespace characters. If the user enters his name in the requested format of firstname followed by a space character, followed by lastname, there should be a match contained in the TestString variable. The groups are held, respectively, in the special variables $1, $2, and $3:

TestString = InputBox(“Enter your name below, in the form” & VBCrLf & _

“first name, then a space then last name.” & VBCrLf & “Don’t enter an initial or middle name.”)

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Regular Expressions and VBScript

You can use the $3, $2, and $1 variables in the replace operation, as follows:

Match = myRegexp.Replace(TestString, “$3,$2$1”)

Because the last name should be contained in $3 and the first name contained in $1, you can reverse those and add a comma using the pattern $3, $2$1. If you wanted to standardize on a single space character in the output (rather than echoing whatever whitespace the user entered into the input box), you could alter the pattern to $3, $1.

The If statement controls whether a message about a successful match is displayed or a message indicating that the user didn’t enter a valid name is displayed:

If Match <> “” Then

MsgBox “Your name in last name, first name format is:” & VBCrLf & Match Else

MsgBox “You didn’t enter your name.” & VBCrLF & “Press OK then F5 to run the example again.”

End If

The RegExp Object’s Execute() Method

The RegExp object’s Execute() method executes regular expression matching against a specified string. The regular expression pattern is held as the value of the RegExp object’s Pattern property. The Execute() method returns a Matches collection, which contains a Match object for each match in the string being tested.

Try It Out

The Execute() Method

The test file, ExecuteDemo.html, is shown here:

<html>

<head>

<title>Demo of the Execute() Method</title> <script language=”vbscript” type=”text/vbscript”> Function ExecuteDemo

Dim myRegExp, TestName, Match, Matches, displayString displayString = “”

Set myRegExp = new RegExp myRegExp.Pattern = “[A-Z]\d” myRegExp.IgnoreCase = True myRegExp.Global = False

TestString = InputBox(“Enter characters and numbers in the text box below.”) Set Matches = myRegexp.Execute(TestString)

For Each Match in Matches

displayString = displayString & “Match found at position “ & Match.FirstIndex & VBCrLf

displayString = displayString & “The match value is ‘“ & Match.Value & “‘.” MsgBox displayString

displayString = “” Next

End Function

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</script>

</head>

</body>

</html>

1.Open ExecuteDemo.html in Internet Explorer, and in the text box within the input box, enter the character sequence A9.

2.Click the OK button, and inspect the text displayed in the message box, as shown in Figure 20-8. Notice that the match is said to occur at position 0, indicating that character positions are numbered from zero.

Figure 20-8

3.Click OK, and press F5 to reload the page and run the script again.

4.In the text box within the input box, enter the character sequence A9 A10 A11 A12 A13.

5.Click the OK button, and inspect the text displayed in the message box, as shown in Figure 20-9. Notice that the result displayed is the same as before. This is so because the value of the myRegExp.Global property is set to False. (In a moment, you will repeat this example, but with the myRegExp.Global property set to True.)

Figure 20-9

How It Works

When the Web page loads, the ExecuteDemo function is called:

First, the variables used in ExecuteDemo are dimensioned:

Function ExecuteDemo

Dim myRegExp, TestName, Match, Matches, displayString

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Regular Expressions and VBScript

The value of the displayString variable is set to the empty string, and a reference to a new RegExp object is set:

displayString = “”

Set myRegExp = new RegExp

The regular expression pattern [A-Z]\d, which matches an alphabetic character followed by a numeric digit, is assigned to the myRegExp object’s Pattern property of the myRegExp object:

myRegExp.Pattern = “[A-Z]\d”

The IgnoreCase property is set to True, which means that the matching process will be case insensitive:

myRegExp.IgnoreCase = True

The value of the Global property is set to False. This means that the Execute() method will return only one match:

myRegExp.Global = False

Input from the user is sought using the InputBox() function, and the input is assigned to the

TestString variable:

TestString = InputBox(“Enter characters and numbers in the text box below.”)

The Execute() method is used to produce a Matches collection:

Set Matches = myRegexp.Execute(TestString)

Each Match in the Matches collection is then processed in a For Each loop. If there is no match, this loop produces no displayed output. The displayString variable is used to construct a string for display:

For Each Match in	Matches
displayString =	displayString & “Match found at position “ & Match.FirstIndex &
VBCrLf
displayString =	displayString & “The match value is ‘“ & Match.Value & “‘.”

Then the MsgBox function is used to display the value of the displayString variable:

MsgBox displayString

Finally, the value of the displayString variable is again set to the empty string, ready to be used in the next iteration of the For Each loop. If the value of the displayString variable was not reset to the empty string, the information from each match would be concatenated into one long display string. You may prefer that approach, which, when the value of the Global property is set to True, will display the information about all Match objects in the Matches collection in a single message box:

displayString = “” Next

End Function

The following example modifies the code so that all matches in the test string are returned.

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Try It Out

The Execute() Method with Global Equal to True

The test file, ExecuteDemoGlobal.html, is shown here:

<html>

<head>

<title>Demo of the Execute() Method</title> <script language=”vbscript” type=”text/vbscript”> Function ExecuteDemo

Dim myRegExp, TestName, Match, Matches, displayString displayString = “”

Set myRegExp = new RegExp myRegExp.Pattern = “[A-Z]\d” myRegExp.IgnoreCase = True myRegExp.Global = True

TestString = InputBox(“Enter characters and numbers in the text box below.”) Set Matches = myRegexp.Execute(TestString)

For Each Match in Matches

displayString = displayString & “Match found at position “ & Match.FirstIndex &

“.”

displayString = displayString & “The match value is ‘“ & Match.Value & “‘.” & VBCrLf

‘displayString = “” Next

MsgBox displayString End Function

</script>

</head>

</body>

</html>

1.Open the file ExecuteDemoGlobal.html in Internet Explorer.

2.Enter the test string A9 A10 A11 A12 A13 into the input box.

3.Click the OK button, and inspect the results displayed in the message box, as shown in Figure 20-10. Notice that each match in the Matches collection is now listed in the message box.

Figure 20-10

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Regular Expressions and VBScript

How It Works

The code works similarly to the code in ExecuteDemo.html. The crucial difference is that the value of the myRegExp variable’s Global property is set to a value of True:

myRegExp.Global = True

This means that the Execute() method will return all matches found. For each match, a Match object will be returned in the Matches collection. As Figure 20-10 shows, there are five matches on this occasion.

Using the Match Object and the Matches

Collection

The Matches collection and its contained Match objects can be created only by using the Execute() method, described in the previous section.

Each Match object has three read-only properties:

FirstIndex — The position of the first character in a match

Length — The length of the match

Value — The value of the match

These contain information about the value of the match, where its first character is located, and the length of the matching character sequence.

The use of the FirstIndex and Value properties was demonstrated in the examples using the Execute() method in the preceding section.

The test file, MatchLength.html, is shown here:

<html>

<head>

<title>The Length Property of a Match Object</title> <script language=”vbscript” type=”text/vbscript”> Function MatchLength

Dim myRegExp, TestName, Match, Matches, displayString displayString = “”

Set myRegExp = new RegExp myRegExp.Pattern = “[A-Z]\d+” myRegExp.IgnoreCase = True myRegExp.Global = True

TestString = InputBox(“Enter characters and numbers in the text box below.”) Set Matches = myRegexp.Execute(TestString)

For Each Match in Matches

displayString = displayString & “Match found at position “ & Match.FirstIndex &

“.”

displayString = displayString & “The match value is ‘“ & Match.Value & “‘.” & VBCrLf

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displayString = displayString & “Its length is “ & Match.Length & “ characters.” &VBCrLf & VBCrLf

‘displayString = “” Next

MsgBox displayString End Function

</script>

</head>

</body>

</html>

Try It Out

The Length Property

1.Open MatchLength.html in Internet Explorer.

2.Enter the following character sequence into the text box of the input box: A9 B10 C110 D1123456 E1234567890 A3.

3.Click the OK button, and inspect the results displayed in the message box, as shown in Figure 20-11.

Figure 20-11

How It Works

When the Web page loads, the MatchLength function is called:

The regular expression pattern assigned to the Pattern property:

myRegExp.Pattern = “[A-Z]\d+”

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matches a single alphabetic character of any case, because the value of the IgnoreCase property is set to True, followed by one or more numeric digits:

myRegExp.IgnoreCase = True

The test string, A9 B10 C110 D1123456 E1234567890 A3, contains six matches. Because the value of the myRegExp variable’s Global property is set to True, all six matches are represented as Match objects in the Matches collection:

myRegExp.Global = True

The Matches collection is created when the following line of code is executed:

Set Matches = myRegexp.Execute(TestString)

The Execute() method creates the Matches collection, which, in this example, contains six Match objects, each of which is processed in the same way as specified in the following For Each loop:

For Each Match in Matches

displayString = displayString & “Match found at position “ & Match.FirstIndex &

“.”

displayString = displayString & “The match value is ‘“ & Match.Value & “‘.” & VBCrLf

displayString = displayString & “Its length is “ & Match.Length & “ characters.” &VBCrLf & VBCrLf

‘displayString = “” Next

The displayString variable initially holds the empty string. Each time through the For Each loop, information is added to the displayString variable about the position of the match (as held in the FirstIndex property) and the length of the match (held in the Length property).

Finally, the value of the displayString variable is displayed in a message box, which displays information about the position and length of each match:

MsgBox displayString

Suppor ted Metacharacters

The following table summarizes the metacharacters supported in VBScript.

Metacharacter	Description

^	Matches the position at the beginning of an input string.
$	Matches the position at the end of an input string.
?	A quantifier. It matches when there is zero or one occurrence of the
	preceding character or group.

	Table continued on following page

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