Using regular expressions in hit attributes

In many situations, the start and end tags of a hit attribute cannot provide an exclusive and unique match to an item of interest on the page. For example, suppose you have the following HTML on the page:

<error id="35">Coupon Code is invalid<\error>

In the above case, the value for the id may change with each message. As a result, a basic hit attribute cannot be constructed to retrieve this error message every time.

Optionally, you can apply a regular expression to the strings that are matched by the hit attribute. After the hit attribute beginning and end tags found one or more matches in the scanned text, the optional regular expression can be applied to the matching strings to further refine the results, returning one, or more values for the hit attribute after the regular expression was applied.

When configuring a hit attribute as an event condition, the Match Count and Hit Attribute Found operators are based on the number of values that are returned by the hit attribute after the regular expression was applied.

• See Limitations in the use of regular expressions in hit attributes.

Suppose the hit attribute is defined with the following tags:

• Start tag: <error id="
• End tag: </error>

In a hit, the following error messages are detected by the hit attribute:

<error id="35">Coupon Code is invalid<\error>
<error id="15">Please enter a zip code<\error>
<error id="12">Please enter a state<\error>
<error id="13">The credit card is invalid<\error>

Suppose you wanted the hit attribute to track error messages on the page where a required text entry was not provided at all. If these messages begin with Please enter, the regular expression matches this string:

^Please enter

In the above example, the regular expression matches errors 12 and 15. If the event specifies to record the match count, the count is 2.

• The first returned value is Please enter a zip code, and the second/last value is Please enter a state.
• If a regular expression is not applied to the above set, the match count is four. The first value is 35">Coupon Code is invalid, and the last value is 13">The credit card is invalid.
  Note: When using the hit attribute as a condition in an event, the values that are returned after the regular expression was applied are available for the evaluation.

After you defined the regular expression, you can test the hit attribute in the Event Tester. See Event Tester.

If the configured hit attribute was functioning properly, you could create a copy of it and modify the regular expression to detect invalid entry error messages. If these messages all end with invalid, the following regular expression matches the string:

invalid$

In the above example, the regular expression matches errors 13 and 35.