Code Assist

AI-Assisted ServiceNow Code Generation

Overview

This skill covers AI-assisted code generation for the core ServiceNow server-side and client-side scripting artifacts:

• Business rules (sys_script): Server-side logic triggered by database operations
• Client scripts (sys_script_client): Browser-side logic for form interactions
• Script includes (sys_script_include): Reusable server-side JavaScript libraries
• UI scripts (sys_ui_script): Global client-side JavaScript libraries
• Applying ServiceNow scripting best practices and API conventions
• Generating code with proper GlideRecord, GlideSystem, and GlideAjax patterns

When to use: When creating new server or client scripts, refactoring existing code, implementing business logic, or generating boilerplate for common ServiceNow patterns.

Prerequisites

• Roles: admin or personalize_script for business rules; admin for script includes
• Access: sys_script, sys_script_include, sys_ui_script, sys_script_client tables
• Knowledge: JavaScript, ServiceNow scripting APIs (GlideRecord, GlideSystem, GlideAjax)
• Related Skills: Complete development/code-review for validation after generation

Procedure

Step 1: Understand ServiceNow Script Types

Key Tables:

Step 2: Generate a Business Rule

MCP Approach - Create a before business rule:

Tool: SN-Create-Record
Parameters:
  table_name: sys_script
  data:
    name: "Validate Priority on Critical Incidents"
    collection: incident
    when: before
    order: 100
    active: true
    filter_condition: priority=1
    action_insert: true
    action_update: true
    action_delete: false
    action_query: false
    script: |
      (function executeRule(current, previous) {
        // Ensure critical incidents have an assignment group
        if (!current.assignment_group) {
          current.assignment_group.setDisplayValue('Service Desk');
          gs.addInfoMessage('Assignment group set to Service Desk for critical incident');
        }

        // Set SLA tracking
        if (current.isNewRecord()) {
          current.sla_due = gs.daysAgoEnd(-1); // Due in 1 day
        }
      })(current, previous);

REST Alternative:

curl -u "$SN_USER:$SN_PASS" \
  "$SN_INSTANCE/api/now/table/sys_script" \
  -H "Content-Type: application/json" \
  -H "Accept: application/json" \
  -X POST \
  -d '{
    "name": "Validate Priority on Critical Incidents",
    "collection": "incident",
    "when": "before",
    "order": 100,
    "active": true,
    "action_insert": true,
    "action_update": true,
    "script": "(function executeRule(current, previous) {\n  if (!current.assignment_group) {\n    current.assignment_group.setDisplayValue(\"Service Desk\");\n  }\n})(current, previous);"
  }'

Step 3: Generate Business Rule Patterns

After business rule - send notification:

Tool: SN-Create-Record
Parameters:
  table_name: sys_script
  data:
    name: "Notify on High Priority Change"
    collection: change_request
    when: after
    order: 200
    active: true
    action_insert: true
    action_update: true
    script: |
      (function executeRule(current, previous) {
        // Only trigger when priority changes to high
        if (current.priority.changesTo(1) || current.priority.changesTo(2)) {
          var assignmentGroup = current.assignment_group.getDisplayValue();
          gs.eventQueue('change.high_priority', current, assignmentGroup, current.number);
        }
      })(current, previous);

Async business rule - heavy processing:

Tool: SN-Create-Record
Parameters:
  table_name: sys_script
  data:
    name: "Sync CMDB Relationships on Insert"
    collection: cmdb_ci_business_app
    when: async
    order: 100
    active: true
    action_insert: true
    script: |
      (function executeRule(current, previous) {
        // Async - runs in background, safe for heavy operations
        var relSync = new CMDBRelationshipSync();
        relSync.syncRelationships(current.sys_id);

        // Update related records
        var gr = new GlideRecord('cmdb_rel_ci');
        gr.addQuery('parent', current.sys_id);
        gr.query();
        while (gr.next()) {
          gr.setValue('validated', true);
          gr.update();
        }
      })(current, previous);

Step 4: Generate a Client Script

onChange client script:

MCP Approach:

Tool: SN-Create-Record
Parameters:
  table_name: sys_script_client
  data:
    name: "Set Impact from Category"
    table: incident
    type: onChange
    fieldname: category
    active: true
    ui_type: 0
    script: |
      function onChange(control, oldValue, newValue, isLoading) {
        if (isLoading || newValue === '') {
          return;
        }

        // Map category to impact
        var impactMap = {
          'network': '1',
          'hardware': '2',
          'software': '3',
          'inquiry': '3'
        };

        var impact = impactMap[newValue] || '3';
        g_form.setValue('impact', impact);

        if (newValue === 'network') {
          g_form.setMandatory('cmdb_ci', true);
          g_form.showFieldMsg('cmdb_ci', 'Configuration item is required for network issues', 'info');
        } else {
          g_form.setMandatory('cmdb_ci', false);
          g_form.hideFieldMsg('cmdb_ci');
        }
      }

onLoad client script:

Tool: SN-Create-Record
Parameters:
  table_name: sys_script_client
  data:
    name: "Initialize Form Defaults"
    table: incident
    type: onLoad
    active: true
    ui_type: 0
    script: |
      function onLoad() {
        // Only apply to new records
        if (!g_form.isNewRecord()) {
          return;
        }

        // Set default contact type
        g_form.setValue('contact_type', 'self-service');

        // Hide fields not needed for self-service
        g_form.setVisible('caller_id', false);

        // Make description mandatory
        g_form.setMandatory('description', true);

        // Add informational message
        g_form.addInfoMessage('Please provide detailed information to help us resolve your issue quickly.');
      }

onSubmit client script:

Tool: SN-Create-Record
Parameters:
  table_name: sys_script_client
  data:
    name: "Validate Before Submit"
    table: incident
    type: onSubmit
    active: true
    ui_type: 0
    script: |
      function onSubmit() {
        // Validate short description length
        var shortDesc = g_form.getValue('short_description');
        if (shortDesc.length < 10) {
          g_form.showFieldMsg('short_description', 'Please provide a more detailed summary (at least 10 characters)', 'error');
          return false;
        }

        // Confirm high priority submission
        var priority = g_form.getValue('priority');
        if (priority === '1') {
          return confirm('You are submitting a Critical priority incident. This will trigger immediate notifications. Continue?');
        }

        return true;
      }

Step 5: Generate a Script Include

Standard script include (class-based):

MCP Approach:

Tool: SN-Create-Record
Parameters:
  table_name: sys_script_include
  data:
    name: "IncidentUtils"
    api_name: "global.IncidentUtils"
    client_callable: false
    active: true
    access: package_private
    script: |
      var IncidentUtils = Class.create();
      IncidentUtils.prototype = {
        initialize: function() {
        },

        /**
         * Get the count of open incidents for a given CI
         * @param {string} ciSysId - The sys_id of the configuration item
         * @returns {number} Count of open incidents
         */
        getOpenIncidentCount: function(ciSysId) {
          var ga = new GlideAggregate('incident');
          ga.addQuery('cmdb_ci', ciSysId);
          ga.addQuery('state', 'IN', '1,2,3');
          ga.addAggregate('COUNT');
          ga.query();
          if (ga.next()) {
            return parseInt(ga.getAggregate('COUNT'), 10);
          }
          return 0;
        },

        /**
         * Auto-assign incident based on category and location
         * @param {GlideRecord} incident - The incident GlideRecord
         * @returns {string} sys_id of the assigned group
         */
        autoAssign: function(incident) {
          var gr = new GlideRecord('sys_user_group');
          gr.addQuery('type', incident.category);
          gr.addQuery('active', true);
          gr.setLimit(1);
          gr.query();
          if (gr.next()) {
            incident.assignment_group = gr.sys_id;
            return gr.sys_id.toString();
          }
          return null;
        },

        type: 'IncidentUtils'
      };

GlideAjax-callable script include:

Tool: SN-Create-Record
Parameters:
  table_name: sys_script_include
  data:
    name: "IncidentAjax"
    api_name: "global.IncidentAjax"
    client_callable: true
    active: true
    script: |
      var IncidentAjax = Class.create();
      IncidentAjax.prototype = Object.extendsObject(AbstractAjaxProcessor, {

        /**
         * Get open incident count for a CI (callable from client)
         */
        getOpenCount: function() {
          var ciSysId = this.getParameter('sysparm_ci_sys_id');
          var utils = new IncidentUtils();
          var count = utils.getOpenIncidentCount(ciSysId);
          return count.toString();
        },

        /**
         * Validate if a user can be assigned to an incident
         */
        validateAssignee: function() {
          var userId = this.getParameter('sysparm_user_id');
          var gr = new GlideRecord('sys_user');
          if (gr.get(userId)) {
            var result = {};
            result.valid = gr.active.toString() === 'true';
            result.name = gr.getDisplayValue();
            result.hasRole = gr.hasRole('itil');
            return JSON.stringify(result);
          }
          return JSON.stringify({valid: false});
        },

        type: 'IncidentAjax'
      });

Step 6: Generate a UI Script

MCP Approach:

Tool: SN-Create-Record
Parameters:
  table_name: sys_ui_script
  data:
    name: "CustomFormHelpers"
    global: true
    active: true
    ui_type: 0
    script: |
      /**
       * Custom form helper utilities
       * Available globally on all forms
       */
      var CustomFormHelpers = {

        /**
         * Call a GlideAjax script include and handle response
         * @param {string} scriptInclude - Name of the script include
         * @param {string} method - Method name to call
         * @param {object} params - Key-value pairs of parameters
         * @param {function} callback - Callback function receiving the answer
         */
        ajaxCall: function(scriptInclude, method, params, callback) {
          var ga = new GlideAjax(scriptInclude);
          ga.addParam('sysparm_name', method);
          for (var key in params) {
            if (params.hasOwnProperty(key)) {
              ga.addParam(key, params[key]);
            }
          }
          ga.getXMLAnswer(function(answer) {
            if (callback && typeof callback === 'function') {
              callback(answer);
            }
          });
        },

        /**
         * Show a confirmation dialog with custom message
         * @param {string} message - Message to display
         * @param {function} onConfirm - Callback on confirm
         * @param {function} onCancel - Callback on cancel
         */
        confirmAction: function(message, onConfirm, onCancel) {
          var dialog = new GlideDialogWindow('glide_confirm_standard');
          dialog.setTitle('Confirm Action');
          dialog.setBody(message);
          dialog.setPreference('onPromptComplete', onConfirm);
          dialog.setPreference('onPromptCancel', onCancel || function() {});
          dialog.render();
        }
      };

Step 7: Deploy and Validate

Verify the created script:

MCP Approach:

Tool: SN-Query-Table
Parameters:
  table_name: sys_script
  query: name=Validate Priority on Critical Incidents
  fields: sys_id,name,collection,when,active,script
  limit: 1

REST Alternative:

curl -u "$SN_USER:$SN_PASS" \
  "$SN_INSTANCE/api/now/table/sys_script?sysparm_query=name=Validate Priority on Critical Incidents&sysparm_fields=sys_id,name,collection,when,active" \
  -H "Accept: application/json"

Tool Usage

Best Practices

• Use before rules for validation: Validate and modify data before it reaches the database
• Use after rules for side effects: Notifications, event triggers, and updates to other records
• Use async rules for heavy operations: GlideRecord loops, external integrations, bulk updates
• Avoid DOM manipulation in client scripts: Use g_form API methods instead of direct DOM access
• Minimize GlideRecord queries in client scripts: Use GlideAjax to call server-side logic
• Wrap business rule scripts in IIFE: Use (function executeRule(current, previous) { ... })(current, previous);
• Check isLoading in onChange: Always return early if isLoading is true to avoid interference during form load
• Use script includes for reusable logic: Never duplicate code across business rules
• Set appropriate order values: Lower numbers execute first; use 100-increment spacing for future insertions
• Scope scripts properly: Use scoped application API (e.g., x_myapp.MyScriptInclude) for custom applications
• Add JSDoc comments: Document parameters, return types, and side effects

Troubleshooting

Business Rule Not Firing

Symptom: Business rule script does not execute Causes:

1. Rule inactive
2. Wrong when setting (before/after/async)
3. Filter condition not matching
4. Action flags (insert/update/delete) not set Solution:

Tool: SN-Query-Table
Parameters:
  table_name: sys_script
  query: name=[rule_name]
  fields: sys_id,name,active,when,collection,action_insert,action_update,filter_condition

Client Script Not Running

Symptom: Client script does not fire on form Causes:

1. Script inactive
2. Wrong type (onLoad/onChange/onSubmit)
3. Missing fieldname for onChange scripts
4. UI type mismatch (desktop vs. mobile vs. both) Solution:

Tool: SN-Query-Table
Parameters:
  table_name: sys_script_client
  query: name=[script_name]
  fields: sys_id,name,active,type,table,fieldname,ui_type

Script Include Not Found

Symptom: "Class not found" or "is not defined" errors Causes:

1. Script include inactive
2. Name mismatch (case-sensitive)
3. Scope access restrictions
4. client_callable not set for GlideAjax calls Solution:

Tool: SN-Query-Table
Parameters:
  table_name: sys_script_include
  query: name=[include_name]
  fields: sys_id,name,active,client_callable,api_name,access

GlideAjax Returns Empty

Symptom: GlideAjax callback receives empty or undefined answer Cause: Script include method does not return a value, or client_callable is false Solution: Verify the script include has client_callable: true and the method returns a string value.

Examples

Example: Complete Feature - Auto-Assignment with Client Feedback

# 1. Create server-side logic (Script Include)
Tool: SN-Create-Record
Parameters:
  table_name: sys_script_include
  data:
    name: "AutoAssignmentEngine"
    client_callable: true
    active: true
    script: |
      var AutoAssignmentEngine = Class.create();
      AutoAssignmentEngine.prototype = Object.extendsObject(AbstractAjaxProcessor, {
        getSuggestedGroup: function() {
          var category = this.getParameter('sysparm_category');
          var location = this.getParameter('sysparm_location');
          var gr = new GlideRecord('sys_user_group');
          gr.addQuery('type', category);
          gr.addQuery('active', true);
          gr.setLimit(1);
          gr.query();
          if (gr.next()) {
            return JSON.stringify({sys_id: gr.sys_id.toString(), name: gr.getDisplayValue()});
          }
          return JSON.stringify({sys_id: '', name: ''});
        },
        type: 'AutoAssignmentEngine'
      });

# 2. Create client script to call it
Tool: SN-Create-Record
Parameters:
  table_name: sys_script_client
  data:
    name: "Auto-suggest Assignment Group"
    table: incident
    type: onChange
    fieldname: category
    active: true
    script: |
      function onChange(control, oldValue, newValue, isLoading) {
        if (isLoading || newValue === '') return;
        var ga = new GlideAjax('AutoAssignmentEngine');
        ga.addParam('sysparm_name', 'getSuggestedGroup');
        ga.addParam('sysparm_category', newValue);
        ga.addParam('sysparm_location', g_form.getValue('location'));
        ga.getXMLAnswer(function(answer) {
          var result = JSON.parse(answer);
          if (result.sys_id) {
            g_form.setValue('assignment_group', result.sys_id, result.name);
            g_form.addInfoMessage('Auto-assigned to: ' + result.name);
          }
        });
      }

# 3. Create business rule as fallback
Tool: SN-Create-Record
Parameters:
  table_name: sys_script
  data:
    name: "Ensure Assignment Group on Insert"
    collection: incident
    when: before
    action_insert: true
    active: true
    script: |
      (function executeRule(current, previous) {
        if (!current.assignment_group) {
          var engine = new AutoAssignmentEngine();
          var result = engine.autoAssign(current);
          if (!result) {
            current.assignment_group.setDisplayValue('Service Desk');
          }
        }
      })(current, previous);

Related Skills

• development/code-review - Review generated code for quality and security
• admin/workflow-creation - Building workflows that complement scripts
• catalog/variable-management - Catalog scripts for service catalog items
• security/acl-management - Security rules that work alongside business rules