Adobe plug-in: getPreviousValue

The getPreviousValue plug-in allows you to set a variable to a value set on a previous hit. This plug-in is not necessary if your implementation contains all desired values in the current hit.

Install the plug-in using the Adobe Experience Platform Launch extension

Adobe offers an extension that allows you to use most commonly-used plug-ins.

1. Log in to launch.adobe.com using your AdobeID credentials.
2. Click the desired property.
3. Go to the Extensions tab, then click on the Catalog button
4. Install and publish the Common Analytics Plugins extension
5. If you haven’t already, create a rule labeled “Initialize Plug-ins” with the following configuration:
   • Condition: None
   • Event: Core – Library Loaded (Page Top)
6. Add an action to the above rule with the following configuration:
   • Extension: Common Analytics Plugins
   • Action Type: Initialize getPreviousValue
7. Save and publish the changes to the rule.

Install the plug-in using Launch custom code editor

If you do not want to use the plug-in extension, you can use the custom code editor.

1. Log in to launch.adobe.com using your AdobeID credentials.
2. Click on the desired property.
3. Go to the Extensions tab, then click the Configure button under the Adobe Analytics extension.
4. Expand the Configure tracking using custom code accordion, which reveals the Open Editor button.
5. Open the custom code editor and paste the plug-in code provided below into the edit window.
6. Save and publish the changes to the Analytics extension.

Install the plug-in using AppMeasurement

Copy and paste the following code anywhere in the AppMeasurement file after the Analytics tracking object is instantiated (using s_gi). Preserving comments and version numbers of the code in your implementation helps Adobe with troubleshooting any potential issues.

/******************************************* BEGIN CODE TO DEPLOY *******************************************/
/* Adobe Consulting Plugin: getPreviousValue v2.0 */
s.getPreviousValue=function(v,c){var s=this,d;c=c||"s_gpv";var b=new Date;b.setTime(b.getTime()+18E5);s.c_r(c)&&(d=s.c_r(c)); v?s.c_w(c,v,b):s.c_w(c,d,b);return d};
/******************************************** END CODE TO DEPLOY ********************************************/

Use the plug-in

The getPreviousValue method uses the following arguments:

• v (string, required): The variable that has the value that you want to pass over to the next image request. A common variable used is s.pageName to retrieve the previous page value.
• c (string, optional): The name of the cookie that stores the value. If this argument is not set, it defaults to "s_gpv".

When you call this method, it returns the string value contained in the cookie. The plug-in then resets the cookie expiration, and assigns it the variable value from the v argument. The cookie expires after 30 minutes of inactivity.

Example Calls

Example #1

The following code…

s.prop7=s.getPreviousValue(s.pageName,"gpv_Page")

• First sets s.prop7 equal to the value passed into s.pageName in the previous image request (i.e. the value stored in the “gpv_Page” cookie)
• The code will then reset the “gpv_Page” cookie, making it equal to the current value of s.pageName
• If s.pageName is not set at the time this code runs, then the code will reset the expiration for the cookie’s current value

Example #2

The following code sets s.prop7 equal to the last value passed into s.pageName, but only if event1 is also contained within s.events, as determined via the inList plug-in, at the time the call takes place.

if(s.inList(s.events,"event1")) s.prop7=s.getPreviousValue(s.pageName,"gpv_Page");

Example #3

The following code sets s.prop7 equal to the last value passed into s.pageName but only if s.pageName is currently set on the page at the same time.

if(s.pageName) s.prop7=s.getPreviousValue(s.pageName,"gpv_Page");

Example #4

The following code sets s.eVar10 equal to the value passed into s.eVar1 in the previous image request. The previous eVar1 value would have been contained in the “s_gpv” cookie. The code will then set the “s_gpv” cookie equal to the current value of s.eVar1.

s.eVar10 = s.getPreviousValue(s.eVar1)

Unlikely Quirks

If the variable associated with the v argument is set to a new value and the getPreviousValue plug-in runs BUT an Analytics server call is NOT sent at the same time, the new v argument value will still be considered the “previous value” the next time the plug-in runs.
For example, assume the following code runs on the first page of the visit:

s.pageName="home"
s.prop7=s.getPreviousValue(s.pageName,"gpv_Page")
s.t();

This code would produce a server call where the pageName argument is equal to “home” and the p7 (prop7) argument is not set. However, the call to s.getPreviousValue would store the value of s.pageName (i.e. “home”) in the cookie specified in the call (i.e. the “gpv_Page” cookie).
Now, assume that immediately afterwards, on the same page, the following code runs (for whatever reason):

s.pageName="happy value"
s.prop7=s.getPreviousValue(s.pageName,"gpv_Page")

Since the s.t() function does not run in this code block, another image request will not be created. However, when the s.getPreviousValue() function code runs this time, s.prop7 will be set equal to the previous value of s.pageName (i.e. “home”) and then will store the new value of s.pageName (i.e. “happy value”) in the “gpv_Page” cookie.
Assume the visitor navigates to a different page and the following code runs on this page:

s.pageName="page 2"
s.prop7=s.getPreviousValue(s.pageName,"gpv_Page")
s.t();

When the s.t() call function runs, it will create an image request where s.pageName=“page 2” and s.prop7 is equal to “happy value”, which was the value of s.pageName when the last call to getPreviousValue took place. The s.prop7 value of “home” was never contained in any real image request even though “home” was the first value passed into s.pageName.

Version History

v2.0 (October 7, 2019)

• Point release (complete logic rewrite).