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The simple web page contains JavaScript code.

The JavaScript variable

myRegExp

is assigned the literal regular expression pattern

L

, using the following

declaration and assignment statement:

var myRegExp = /L/;

In JavaScript, the forward slash is used to delimit a regular expression pattern in a way similar to how

paired quotes are used to delimit a string. There is an alternate syntax, which is not discussed here.

When you click the button labeled Click Here to Enter Text, the

ShowPrompt()

function is called.

The

entry

variable is used to collect the string you enter in the prompt box:

var entry = prompt(“This script tests for matches for the regular expression

pattern: “ + myRegExp + “.\nType in a string and click on the OK button.”, “Type

your text here.”);

The output created depends on whether or not the text you entered contains a match for the regular expres-

sion pattern. Once the text has been entered and the OK button clicked, an

if

statement is executed, which

checks whether or not the text you entered (and which is stored in the

entry

variable) contains a match for

the regular expression pattern stored in the variable

myRegExp

:

if (Validate(entry)){

The

if

statement causes the

Validate

function to be called:

function Validate(entry){

return myRegExp.test(entry);

} // end function Validate()

The

test()

method of the

myRegExp

variable is used to determine whether or not a match is present.

If the

if

statement

if (Validate(entry))

returns the Boolean value

true

, the following code is executed

alert(“There is a match!\nThe regular expression pattern is: “ + myRegExp + “.\n

The string that you entered was: ‘“ + entry + “‘.”);

and uses the

myRegExp

and

entry

variables to display the regular expression pattern and the string that

you entered, together with explanatory text.

If there is no match, the following code is executed, because it is contained in the

else

clause of the

if

statement:

alert(“There is no match in the string you entered.\n” + “The regular expression

pattern is “ + myRegExp + “\n” + “You entered the string: ‘“ + entry + “‘.” );

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Appendix A: Simple Regular Expressions

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