Save a versioned validated envelope
See this course’s project requirements
A fictional local reading-list app with versioned saved data, explicit browser-only wording, validated JSON export/import and corrupt-save recovery tests.
Keep your working files in your own notebook or software. Save a private description, checklist, and work link in My Proof.
What to include
- Document the exact storage origin and distinguish reload persistence from account synchronization.
- Retain the validated envelope format and prove an invalid replacement leaves the earlier record intact.
- Demonstrate a rejected corrupt load and a failed write without silently discarding prior data.
- Create and inspect an actual JSON export and state its exact contents.
- Produce a valid/invalid import matrix proving rejected content retains the previous list.
- Deliver a two-tab observation or truthful unavailable note, alongside the validated backup/recovery project.
Review and revise
Use these criteria to check your work and choose what to improve.
- The implementation or declared simulation follows the supplied contract and retains inspectable original inputs.
- Normal, boundary and rejected cases are recorded with expected versus observed results.
- The changed case has a correct explanation and does not rely on hidden state.
- The project includes source, outputs, instructions and honest tool, privacy and verification limits.
Want more background?
The idea in everyday life
Use the supplied reading.html, reading-store.mjs and test-reading.mjs with the invented title Moon Garden. Serve the folder at http://localhost:8765 using python3 -m http.server 8765 --bind 127.0.0.1.
The saved format carries a schema version and revision beside the list. Validation rejects unsupported shape before a write replaces the old record.
Save a versioned validated envelope — original worked practice
The saved format carries a schema version and revision beside the list. Validation rejects unsupported shape before a write replaces the old record.
Use the supplied reading.html, reading-store.mjs and test-reading.mjs with the invented title Moon Garden. Serve the folder at http://localhost:8765 using python3 -m http.server 8765 --bind 127.0.0.1.
1. Step 1
Read decode in reading-store.mjs: version must be 1, revision a nonnegative integer, and items at most 20 nonempty strings of up to 80 characters.
You should see: The accepted saved-data contract is explicit.
The saved format carries a schema version and revision beside the list. Validation rejects unsupported shape before a write replaces the old record.
2. Step 2
Inspect save: JSON.stringify is followed by decode before setItem.
You should see: Invalid data cannot overwrite the previous key through this function.
The saved format carries a schema version and revision beside the list. Validation rejects unsupported shape before a write replaces the old record.
3. Step 3
Add Moon Garden once and inspect the revision in the visible status.
You should see: A successful addition increments the revision.
The saved format carries a schema version and revision beside the list. Validation rejects unsupported shape before a write replaces the old record.
4. Step 4
Run node test-reading.mjs and retain the invalid-item assertion.
You should see: A schema and pre-write validation record.
The saved format carries a schema version and revision beside the list. Validation rejects unsupported shape before a write replaces the old record.
What to finish
Retain the validated envelope format and prove an invalid replacement leaves the earlier record intact.
Watch for this
Deleting an existing record before confirming the replacement schema.
How can I tell I understand it?
Demonstrate the rule: The saved format carries a schema version and revision beside the list. Validation rejects unsupported shape before a write replaces the old record. Use the supplied variant to distinguish a changed result from a broken implementation.
Quick knowledge check
Answer all 3 questions. Get at least 2 right and the lesson completes automatically.
You’ll get an explanation for each answer. Signed in? Your results save to your account.
Pass the check. We’ll save the progress.
Answer all 3 questions above and get at least 2 right. You can review the explanations and try again.
Go to the knowledge checkTools, templates, and lesson sources
Tools and templates
Tools open in a new tab so you can keep your place here.
Sources and further reading
Explore the references behind this lesson.
Source & access notes · checked 2026-10-01
Relevant documented module/API behavior inspected during expansion authoring; actual execution evidence is recorded separately. No grant eligibility is established.
Access: Official page retrieved with the web reader on 2026-10-01. Documentation reading does not certify execution in every native tool or browser.
Reuse: Original local practice files, fictional data, worked examples and questions. Concepts paraphrased and linked; source exercises are not copied.
Report a problem with this lesson
Tell us what went wrong. Please leave out personal information and private project contents.