Best Practices for Writing JavaScript Code in ServiceNow

Writing JavaScript in ServiceNow involves more than simply crafting functional scripts. It requires adherence to best practices to ensure maintainability, performance, and alignment with the platform's capabilities. Below are some guidelines, common pitfalls, and refactoring tips to help you improve your ServiceNow JavaScript development.

1. Follow Naming Conventions

Best Practice:

Use meaningful and consistent naming for variables, functions, and objects. Adopting camelCase for variables and functions and PascalCase for classes is a widely accepted convention.

Example:

// Good
var incidentNumber = "INC0012345";
function getOpenIncidents() {
    // logic
}        

Common Pitfall:

// Poor
var x = "INC0012345";
function OpenIncident() {
    // logic
}        

Why It Matters: Meaningful names make your code more readable and easier to debug.

2. Avoid Hardcoding Values

Best Practice:

Store values in constants or retrieve them dynamically via APIs or system properties.

Refactored Code:

const HIGH_PRIORITY = 1;
var incidents = new GlideRecord("incident");
incidents.addQuery("priority", HIGH_PRIORITY);
incidents.query();        

Common Pitfall:

// Hardcoding
var incidents = new GlideRecord("incident");
incidents.addQuery("priority", 1);
incidents.query();        

Why It Matters: Hardcoded values reduce flexibility and can lead to errors if priorities change.

3. Use GlideRecord Efficiently

Best Practice:

Minimize database queries and fetch only the required fields to enhance performance.

Refactored Code:

var gr = new GlideRecord("incident");
gr.addQuery("state", "1"); // Filter for active incidents
gr.query();
if (gr.next()) {
    gs.info("Incident: " + gr.number);
}        

Common Pitfall:

var gr = new GlideRecord("incident");
gr.query(); // Retrieves all records
while (gr.next()) {
    if (gr.state == "1") {
        gs.info("Incident: " + gr.number);
    }
}        

Why It Matters: Querying unnecessary data strains system resources and can slow down performance.

4. Handle Errors Gracefully

Best Practice:

Include error handling mechanisms to make your scripts robust.

Refactored Code:

try {
    var user = gs.getUserByID("non_existent_user");
    if (!user) throw "User not found";
} catch (error) {
    gs.error("An error occurred: " + error);
}        

Common Pitfall:

// No error handling
var user = gs.getUserByID("non_existent_user");
user.someMethod(); // Throws error if user is null        

Why It Matters: Proper error handling prevents runtime failures and improves debugging.

5. Write Modular Code

Best Practice:

Break down your scripts into reusable functions and classes.

Refactored Code:

function getActiveIncidents() {
    var gr = new GlideRecord("incident");
    gr.addQuery("state", "1");
    gr.query();
    return gr;
}

function logIncidents() {
    var incidents = getActiveIncidents();
    while (incidents.next()) {
        gs.info("Incident: " + incidents.number);
    }
}
logIncidents();        

Common Pitfall:

// Monolithic code
var gr = new GlideRecord("incident");
gr.addQuery("state", "1");
gr.query();
while (gr.next()) {
    gs.info("Incident: " + gr.number);
}        

Why It Matters: Modular code is easier to maintain, test, and extend.

6. Comment Judiciously

Best Practice:

Write comments that add value without cluttering your code.

Example:

// Fetch active incidents
var incidents = new GlideRecord("incident");
incidents.addQuery("state", "1");
incidents.query();        

Common Pitfall:

// Query the incident table
// Add a query for state = 1
// Execute the query
var incidents = new GlideRecord("incident");
incidents.addQuery("state", "1");
incidents.query();        

Why It Matters: Concise and meaningful comments help collaborators without overwhelming them.

7. Optimize for Security

Best Practice:

Avoid exposing sensitive information and validate user input.

Refactored Code:

var userId = gs.getUserID();
if (!gs.hasRole("admin")) {
    gs.error("Unauthorized access by user: " + userId);
    return;
}        

Common Pitfall:

// Missing role validation
var userId = gs.getUserID();
// Execute admin tasks without checks        

Why It Matters: Ensuring security prevents unauthorized access and protects sensitive data.

By following these best practices and avoiding common pitfalls, you can write clean, efficient, and secure JavaScript code in ServiceNow. Consistent adherence to these principles will improve your code's quality and make it easier for others to collaborate with you.