ES5 Compliance for ServiceNow
ServiceNow runs on Mozilla Rhino engine which only supports ES5 JavaScript (2009 standard). All server-side scripts MUST use ES5 syntax.
Forbidden Syntax (WILL CAUSE SyntaxError)
| ES6+ Syntax | ES5 Alternative |
|---|---|
const x = 5 | var x = 5 |
let items = [] | var items = [] |
() => {} | function() {} |
`Hello ${name}` | 'Hello ' + name |
for (x of arr) | for (var i = 0; i < arr.length; i++) |
{a, b} = obj | var a = obj.a; var b = obj.b; |
[a, b] = arr | var a = arr[0]; var b = arr[1]; |
...spread | Use Array.prototype.slice.call() |
class MyClass {} | Use constructor functions |
async/await | Use GlideRecord callbacks |
Promise | Use GlideRecord with callbacks |
Common Patterns
Variable Declarations
javascript// WRONG - ES6 const MAX_RETRIES = 3 let currentUser = gs.getUser() // CORRECT - ES5 var MAX_RETRIES = 3 var currentUser = gs.getUser()
Functions
javascript// WRONG - Arrow functions var active = incidents.filter((inc) => inc.active) var process = () => { return "done" } // CORRECT - ES5 functions var active = [] for (var i = 0; i < incidents.length; i++) { if (incidents[i].active) { active.push(incidents[i]) } } var process = function () { return "done" }
String Concatenation
javascript// WRONG - Template literals var message = `Incident ${number} assigned to ${user}` // CORRECT - String concatenation var message = "Incident " + number + " assigned to " + user
Loops
javascript// WRONG - for...of for (var item of items) { gs.info(item) } // CORRECT - Traditional for loop for (var i = 0; i < items.length; i++) { gs.info(items[i]) }
Default Parameters
javascript// WRONG - Default parameters function process(incident, priority = 3) { // ... } // CORRECT - Manual defaults function process(incident, priority) { if (typeof priority === "undefined") { priority = 3 } // ... }
Automatic Validation
Before deploying any server-side script:
- Check for
const/letdeclarations - convert tovar - Check for arrow functions
=>- convert tofunction() - Check for template literals
`- convert to string concatenation - Check for destructuring
{a, b}- convert to explicit property access - Check for
for...ofloops - convert to index-based loops
Exception: Client Scripts
Client-side scripts (Client Scripts, UI Policies) run in the browser and MAY support ES6+ depending on user's browser. However, for maximum compatibility, ES5 is still recommended.
