Introduction to Scripting in ServiceNow
ServiceNow provides a powerful and flexible scripting environment that allows administrators to automate workflows, customize behaviors, integrate with external systems, and more using JavaScript. Effective use of scripts is key to getting the most out of the platform and meeting unique business requirements. This guide will provide an in-depth overview of scripting best practices, common use cases, and how to structure scripts for maximum reusability and maintainability within ServiceNow.
Getting Started with Scripting
The first step to writing effective scripts is to understand the script include files, global variables, and logger that are available out of the box in the ServiceNow platform. All scripts have access to these resources which handle common tasks like HTTPS requests, SMTP email sending, and logging debug messages.
The gs.include file contains utility functions for common system interactions like retrieving records, making SOAP/REST calls, formatting data, and handling asynchronous processes. The global.gs and debugger.gs files expose global variables and logging functions respectively. Knowing which includes provide necessary functions will help write more succinct code.
Scripts can be created and stored as reusable include files or defined inline within table configurations, workflow actions, and other places that support scripting. Include files are preferred as they can be tested independently and shared between different parts of the system. Files are stored under System Documentation and accessed via gs.include(‘/path/to/file.js’).
Best Practices for ServiceNow Scripting
When designing scripts, it’s important to follow software engineering principles like readability, reusability, testability, and avoid logic duplication. Here are some additional guidelines:
Use consistent formatting, spacing and comments to make code readable at a glance.
Separate script concerns into logical reusable functions rather than one large block.
Validate all incoming parameters and return error objects on failure.
Handle errors gracefully with try/catch blocks and avoid cryptic error messages.
For async workflows, return promises instead of using callbacks to simplify code.
Name variables and functions descriptively based on their purpose rather than position.
Use constants and well-named variables overhardcoding values for easy maintenance.
Split complex processes into multiple smaller scripts for modularity.
Use schema validation when working with records to avoid incorrect data.
Test scripts thoroughly with sample input/output before production deployment.
For performance, minimize script execution frequency through caching where possible.
Apply security best practices like input validation and permission checking.
Sample Workflow Script
Here is an example of a modular workflow script that follows the recommended patterns:
/* Workflow Entry Script */
/* Imports */
const workflowUtils = require(‘workflow_utils’);
/* Constants */
const STAGES = {
PENDING: ‘pending’,
IN_PROGRESS: ‘in_progress’
};
/* Main workflow function */
async function runWorkflow(workflow) {
try {
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/* Validation */
validateWorkflow(workflow);
/* Stage change logic */
if(workflow.stage === STAGES.PENDING) {
await setInProgress(workflow);
}
/* Additional stages */
} catch (err) {
/* Error handling */
handleError(err);
}
}
/* Reusable utility functions */
/**
Validates the incoming workflow object
*/
function validateWorkflow(workflow) {
//…
}
/**
Changes workflow stage to in progress
*/
async function setInProgress(workflow) {
try {
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//…business logic…
return workflowUtils.updateStage(workflow, STAGES.IN_PROGRESS);
} catch (err) {
throw err;
}
}
/* Main execution */
runWorkflow(gs.args.workflow);
This shows separation of validation, stage logic, error handling into logical units for readability and reuse. Globals and includes are used efficiently throughout.
Common Scripting Use Cases
Beyond basic workflow automation, scripts are essential for many complex integrations and custom processes within ServiceNow. Here are some examples:
Data Import/Export: Import large datasets in batches or map external APIs to internal record schemas.
External Integrations: Trigger REST calls during events, sync data with LDAP/databases using outbound scripts.
UI Customizations: Add client-side behaviors, populate dependent picklists, validate fields on form submit etc.
Formulas and Calculations: Complex calculations beyond the out-of-box formula builder like conditional logic, date math etc.
Automated Processes: Scheduled tasks using platfrom APIs for periodic reports, cleanup jobs etc.
Extended Table Logic: Add business rules, calculate fields on changes, cascade updates across related records.
Third-Party Integrations: Interact with external systems like telecom routers, BPM workflows, IoT gateways etc.
Feature Development: Rapidly prototype new features and APIs before full frontend/backend development.
System Management: Backup/restore procedures, encryption handlers, upgrade automation, logging etc.
Legacy System Migrations: Import/transform datasets to map to new ServiceNow schemas during migration.
With JavaScript and REST capabilities, the possibilities are vast. Effective use of design patterns help tackle even the most complex requirements.
Testing and Deployment
Proper testing is crucial before deploying any production scripts. ServiceNow provides a ScriptTest Tool and record/playback functionality in the UI to simulate inputs and validate outputs. Common testing steps include:
Unit test individual functions by passing sample params and asserting results
Integration test full processes by mocking external deps
Parameter testing – validate all expected data types and edge cases
Error handling validation – ensure failures are gracefully caught
Performance testing – Add logging and metrics to check bottlenecks
Compliance testing – Security scans, checking for vulnerabilities
Deploy scripts by importing include files or defining them inline where needed. Avoid pushing unstable code to production. Deploy iteratively with rollbacks and monitor logs/errors closely post-deployment. Configuration management helps track script versions over time.
With careful design, powerful testing frameworks, and modular reusable code, ServiceNow scripts provide an extremely flexible and scalable way to develop advanced custom solutions on the platform. Following best practices ensures scripts remain performant, secure and easy to maintain as requirements evolve over time.
Andrew Stroud