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Hi there,

One of the most common performance scripting mistakes I see on the ServiceNow Community and in customer Instances: the use of setValue() on reference fields/variables within Client-Side scripting. What mistake do I mean? Only providing a sys_id as a second parameter when using setValue().

Let's explain and what to do about this.

The third parameter

When using setValue() on a reference field, be sure to include the reference field displayValue as the third parameter. If you set the value without the displayValue, the ServiceNow instance does a synchronous call to retrieve the display value for the record you specified. This extra round trip to the server can impact performance.

So you might have set up a nice piece of Client-Side scripting, using getReference with a callback, using GlideAjax with getXML, or even better using GlideAjax with getXMLAnswer. Though if you fail to use the third parameter when using setValue(), your effort to perform an efficient lookup is actually wasted.

If you have a perfect performing instance, you will hardly notice the difference. You can just see this, happen though not enjoying enough. If you have a so so performing instance, a less internet connection, working on virtualization software, then this can become very painful.

The correct notation would be:

Incorrect example

Here an examples of incorrect applying setValue. Incorrect because it concerns a reference variable to sys_user, where they are only providing a second parameter with the sys_id:

g_form.setValue('manager',user.manager);

https://community.servicenow.com/community?id=community_question&sys_id=6806a1e8db2350d09e691ea66896...

Additional synchronous call

So what additional synchronous call does the ServiceNow instance perform actually? For example using the Chrome DevTools (F12) in combination with the JavaScript Executor (CTRL+SHIFT+J), you could inspect the Network. Let's take the Incident form as an example, and set the Location reference field with only a second parameter.

Using:

g_form.setValue('location', '25ab9d720a0a0bb300793d3a6b891f82');

Results in:

Notice two requests have been performed. When having a closer look at the second request: the synchronous call which retrieves the display value.

<xml answer="6304 Northwest Barry Road, Kansas City,MO" sysparm_max="15" sysparm_name="getDisplay" sysparm_processor="AjaxClientHelper" sysparm_value="25ab9d720a0a0bb300793d3a6b891f82"/>

So an additional server call is executed, and the additional server call is also executed synchronously! While you might just have tried to setup an efficient Client Side script using callback parameters, etcetera which theoretically is good or - when using GlideAjax with getXMLAnswer - even great. Though missing out on the third parameter… all your efforts to setup an efficient Client Side script just went down the drain! What a waste.

Providing third parameter, value AND displayValue

Let's execute the same, though now while providing a third parameter. A third parameter which represents the displayValue.

Using:

g_form.setValue('location', '25ab9d720a0a0bb300793d3a6b891f82', '6304 Northwest Barry Road, Kansas City,MO');

Results in:

Notice only one request has been performed. The additional synchronous server call mentioned in the previous step did not get executed this time!

Result

A small piece of knowledge, though a valuable one concerning performance. Try it yourself, and try to understand the difference. Again, this is one of the most made mistakes I see on the ServiceNow Community and on customer instances.

Just to mention again, the correct way:

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