The GlideAjax class allows a client-side script to make an AJAX (Asynchronous JavaScript And XML) call to the server, execute a server-side script include, and even return a value. GlideAjax might be one of the least well understood client-side APIs in ServiceNow, in part because it has both a client-side, and a server-side component.

First, let's discuss the server-side component. A GlideAjax call from a client-side script will ultimately execute a script include (which as we learned in a previous chapter, is a server-side script), so let's create a script include for our GlideAjax script to talk to.

For our example, we're going to create a simple script include that'll return the value of a system property we specify, so we'll create a script include called GetPropertyAjax. Once we enter this name and then tab out of the Name field, the default scaffolding of the script include is populated into the Script field.

To make this script include accessible from client-side scripts through...