Error Pages
All Svelte topics∙ Svelte
Error Pages explains route error boundaries rendered from expected or unexpected failures for this error, pages lesson. You will learn its exact Svelte rule, failure mode, verification plan, and production evidence.
Syntax
export const load = async ({ fetch }) => ({ items: await fetch("/api/items") });Example
// Topic: Error Pages
const route = { ssr: true, dataLoaded: true };
console.log(route.ssr && route.dataLoaded ? 'route ready' : 'loading');
// Expected Output: route readyExpected Output
route readyLine-by-line
| Line | Meaning |
|---|---|
const route = { ssr: true, dataLoaded: true }; | Defines state, behavior, or output for this Svelte example. |
console.log(route.ssr && route.dataLoaded ? 'route ready' : 'loading'); | Prints the expected result for this Svelte lesson. |
Real-World Uses
- 1Error Pages is used for full-stack Svelte applications with SSR and deployment adapters.
- 2Its mechanism is route error boundaries rendered from expected or unexpected failures for this error, pages lesson.
- 3Return useful status and safe messages while logging internal details separately. Keep decisions specific to error, pages.
- 4Production code must account for Showing raw exception details leaks implementation information. Do not copy assumptions from a neighboring topic into error, pages.
- 5Teams evaluate it using safe error recovery measured for error, pages.
Common Mistakes
- 1Showing raw exception details leaks implementation information. Do not copy assumptions from a neighboring topic into error, pages.
- 2Implementing Error Pages without understanding route error boundaries rendered from expected or unexpected failures for this error, pages lesson.
- 3Choosing Error Pages where simpler local Svelte code is clearer.
- 4Skipping Test 404, validation error, server failure, nested boundary, and recovery. Include an assertion that directly exercises error, pages.
- 5Optimizing before measuring safe error recovery measured for error, pages.
Best Practices
- 1Return useful status and safe messages while logging internal details separately. Keep decisions specific to error, pages.
- 2Document route error boundaries rendered from expected or unexpected failures for this error, pages lesson in the smallest useful component, store, action, route, or service.
- 3Represent every relevant loading, success, empty, denied, and failure state.
- 4Test 404, validation error, server failure, nested boundary, and recovery. Include an assertion that directly exercises error, pages.
- 5Use safe error recovery measured for error, pages to guide improvements.
How it works
- 1Error Pages relies on route error boundaries rendered from expected or unexpected failures for this error, pages lesson.
- 2Return useful status and safe messages while logging internal details separately. Keep decisions specific to error, pages.
- 3Its main failure mode is Showing raw exception details leaks implementation information. Do not copy assumptions from a neighboring topic into error, pages.
- 4Useful evidence is safe error recovery measured for error, pages.
Implementation decisions
- 1Identify the owning component, store, action, route, load function, or server handler.
- 2Keep state local until multiple owners genuinely need it.
- 3Keep server secrets and validation outside browser components.
- 4Define cleanup for subscriptions, actions, timers, and requests.
Verification plan
- 1Test 404, validation error, server failure, nested boundary, and recovery. Include an assertion that directly exercises error, pages.
- 2Check initial render, assignment-driven updates, user interaction, and cleanup.
- 3Confirm keyboard and screen-reader behavior for visible UI.
- 4Measure production output only after correctness passes.
Practice task
- 1Build the smallest Error Pages example.
- 2Introduce this failure: Showing raw exception details leaks implementation information. Do not copy assumptions from a neighboring topic into error, pages.
- 3Correct it using this rule: Return useful status and safe messages while logging internal details separately. Keep decisions specific to error, pages.
- 4Record safe error recovery measured for error, pages before and after the change.
Quick Summary
- Error Pages works through route error boundaries rendered from expected or unexpected failures for this error, pages lesson.
- Return useful status and safe messages while logging internal details separately. Keep decisions specific to error, pages.
- Avoid Showing raw exception details leaks implementation information. Do not copy assumptions from a neighboring topic into error, pages.
- Test 404, validation error, server failure, nested boundary, and recovery. Include an assertion that directly exercises error, pages.
- Measure success with safe error recovery measured for error, pages.
Interview Questions
Q1. What is Error Pages used for?
Answer: It is used for full-stack Svelte applications with SSR and deployment adapters.
Q2. How does Error Pages work in Svelte?
Answer: It works through route error boundaries rendered from expected or unexpected failures for this error, pages lesson.
Q3. What rule matters most?
Answer: Return useful status and safe messages while logging internal details separately. Keep decisions specific to error, pages.
Q4. What failure is common?
Answer: Showing raw exception details leaks implementation information. Do not copy assumptions from a neighboring topic into error, pages.
Q5. How should it be verified?
Answer: Test 404, validation error, server failure, nested boundary, and recovery. Include an assertion that directly exercises error, pages. Evaluate safe error recovery measured for error, pages.
Quiz
Which practice best supports Error Pages?