Hi @Priya Reddy I , Hopefully that is a URL type variable.

In case if catalog client scripts, you can try the below:

this.location.href

this.location.origin

https://servicenowguru.com/client-scripts-scripting/parse-url-parameters-client-script/ 

OR, try the approach provided here and set the field value by onload or onchange client script

https://www.servicenow.com/community/itsm-forum/how-to-get-system-property-at-client-side/m-p/457070