Setting Catalog Item Variables from URL Parameters - ben-vargas/servicenow-wiki GitHub Wiki

When creating a custom ServiceNow Catalog Item, you may want to pre-populate certain variables based on URL parameters. For example, you might include parameters like sysparm_request_type or sysparm_capability in a custom URL to direct users to a specific Catalog Item view with preselected values.

However, using javascript:RP.getParameterValue('parameter_name') directly in variable default values can fail under certain circumstances—such as when running a multi-step wizard or if the variable is being used in non-Employee Service Center (ESS) contexts.

This article shows how to properly retrieve URL parameters and set variable values on load, ensuring a smoother user experience and consistent behavior regardless of the environment.

Example Scenario

Custom URL Example:

com.glideapp.servicecatalog_cat_item_view.do?sysparm_id=aae7e9606f5221007af78e354b3ee455&sysparm_request_type=Tech%20Ops%20Tools&sysparm_capability=ServiceNow

In this URL:

  • sysparm_request_type and sysparm_capability define values you want to set on variables in the Catalog Item form.
  • Initially, you might try javascript:RP.getParameterValue('sysparm_request_type') in a variable’s default value, but this can fail in certain contexts.

Why javascript:RP.getParameterValue() May Fail

  • Wizards or Non-ESS Scenarios:
    The function RP.getParameterValue() may not always return the expected values when used as a variable default script, especially in a wizard or when accessed outside of the ESS portal.
  • Timing & Rendering Issues:
    The Catalog Item form may load in a manner that prevents these values from being set at the right time, causing empty or incorrect defaults.

Recommended Approach: OnLoad Client Script

Instead of relying on the variable’s default value to pull from URL parameters, use an onLoad Client Script that:

  1. Extracts parameter values from window.location.href.
  2. Cleans and decodes them.
  3. Sets the variable values directly via g_form.setValue().

This approach ensures that the variables are set after the form is fully loaded, increasing reliability.

Example Code (OnLoad Client Script)

Client Script Configuration:

  • Type: OnLoad
  • Applies to your Catalog Item

Script:

function onLoad() {
    // Helper function to retrieve a parameter value from the current URL
    function getParmVal(name) {
        name = name.replace(/[\[]/,"\\[").replace(/[\]]/,"\\]");
        var regexS = "[\\?&]" + name + "=([^&#]*)";
        var regex = new RegExp(regexS);
        
        var results = regex.exec(window.location.href);
        if (results)
            return unescape(results[1]);

        try {
            var topWindow = getTopWindow();
            if (topWindow == window)
                return '';

            results = regex.exec(topWindow.location.href);
            if (results)
                return unescape(results[1]);

            return "";
        } catch (e) {
            jslog('Error in getParmVal: ' + e.name + ': ' + e.message);
        }
    }

    // Attempt to set request_type variable from sysparm_request_type parameter
    var requestType = getParmVal('sysparm_request_type');
    if (requestType) {
        var typeDecoded = requestType.replace(/\+/g, ' ');
        g_form.setValue('request_type', typeDecoded);
    }

    // Attempt to set capability variable from sysparm_capability parameter
    var capability = getParmVal('sysparm_capability');
    if (capability) {
        var capabilityDecoded = capability.replace(/\+/g, ' ');
        g_form.setValue('capability', capabilityDecoded);
    }
}

What This Script Does:

  • getParmVal(name): Extracts the specified parameter from the current page URL or the top window URL. It returns an empty string if the parameter doesn’t exist.
  • Parameter Decoding: The code replaces + signs (URL-encoded spaces) with actual spaces, ensuring a clean, user-friendly value.
  • Setting Variables: Uses g_form.setValue() to assign the decoded parameter values to the request_type and capability variables.

Additional Notes

  • Server-Side AJAX Calls:
    If variables depend on values retrieved from server-side (e.g., via GlideAjax) after setting request_type, consider triggering the server call within the same onLoad script or in an onChange Client Script for the request_type variable.

  • Error Handling & Logging:
    The script uses jslog() for error logging. For debugging, consider adding alert() or console.log() messages (in non-production environments) to verify that parameters are retrieved correctly.

  • Adapting to Other Parameters:
    You can easily adapt this code to pull additional parameters by adding more calls to getParmVal() and using g_form.setValue() on different variables.

Conclusion

By using an onLoad Client Script and parsing URL parameters through window.location.href, you can reliably set Catalog Item variables. This method avoids potential issues with javascript:RP.getParameterValue() in certain scenarios, providing a more robust and user-friendly experience for catalog item configuration.