Hook
Domo CodeEngine functions fail silently by default — and when they do throw, the raw error message that surfaces to the end user is often useless noise. Here's how to fix that.
Why It Matters
Without deliberate error handling, a CodeEngine function either returns nothing meaningful or exposes a raw stack trace to whoever triggered it. For user-facing features — like a button that sets a landing page inside a Domo app — that's a broken experience. Graceful error handling lets you validate inputs early, surface human-readable messages, and distinguish expected failures from unexpected ones. It also makes debugging dramatically faster during development.
What You'll Learn
- Validate function inputs before hitting external APIs and throw descriptive errors on bad arguments
- Structure a CodeEngine JavaScript function with a
try/catchblock that surfaces actionable failure messages - Understand why the default "no logs were written" error output is insufficient and what to emit instead
- Use template literals (F-string equivalent) in JavaScript for cleaner URL construction inside CodeEngine
- Test error paths directly in the CodeEngine UI before wiring a function to a live app
Structuring Error Handling in a CodeEngine JavaScript Function
The example function — setMyLandingPage — accepts an objectId and an objectType string. The first thing it does is validate that objectType is either "card" or "page", since that value gets interpolated directly into the API URL. Without that guard, a bad argument silently produces a malformed request.
The naive starting point most developers ship looks like this: call the URL, return true, hope for the best. No try/catch, no input validation. When it fails, Domo surfaces "standard error out — no logs were written," which tells you nothing actionable.
The corrected pattern:
- Guard at the top — check the input immediately and
throw new Error("objectType must be 'page' or 'card'")before any async work begins. - Wrap the fetch in
try/catch— any network or API error gets caught and re-thrown with a message you control. - Return structured output — the function returns a typed boolean (
isSuccess) so callers have a clear contract to check against.
One practical note: JavaScript typing feels unfamiliar if you come from Python. Inside CodeEngine, JSDoc-style comments at the top of the function (@param {string} objectType) serve as the type contract — they're not enforced at runtime, but they document intent and show up in the CodeEngine UI when teammates inspect the function signature.
The key takeaway is to treat CodeEngine functions the same way you'd treat any public API endpoint: validate inputs first, wrap side effects in error boundaries, and return something meaningful on failure. Your future self — and your users — will thank you.
