The Life Starter
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Course Library · Lesson 6 of 6
Digital · Guided lesson

Package truthful offline verification

About 29 minutes · 7 reading + 22 practice and checks
Time includes reading, practice, and questions. Extra videos or further study are optional.
See this course’s project requirements

A localhost reference-card app with an explicit asset cache, offline fallback, visible cache version and a controlled update/cleanup test.

Keep your working files in your own notebook or software. Save a private description, checklist, and work link in My Proof.

What to include

  • Create an exact cache inventory and a visible list of excluded offline behavior.
  • Record the local secure context and separate worker registration, installation, and page control.
  • Produce cache-entry evidence and a controlled required-asset failure/repair record.
  • Record actual cached reload and failed-network navigation fallback behavior separately.
  • Produce a controlled update/activation record proving the new version and bounded cache cleanup.
  • Deliver source, policy assertions, version evidence, performed browser tests, and scoped cleanup/limits.

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.
Open the full course project
Want more background?
Before you begin

The idea in everyday life

In a fresh dedicated folder place index.html, cards.css, offline.html, sw.mjs, cache-policy.mjs and test-cache.mjs. Serve only that folder with python3 -m http.server 8765 --bind 127.0.0.1 and open http://localhost:8765/index.html.

The idea

Policy assertions, worker lifecycle observations, and offline browser reloads are separate evidence. Cached resources are not guaranteed permanent or a backup of user records.

Follow along

Package truthful offline verification — original worked practice

Policy assertions, worker lifecycle observations, and offline browser reloads are separate evidence. Cached resources are not guaranteed permanent or a backup of user records.

In a fresh dedicated folder place index.html, cards.css, offline.html, sw.mjs, cache-policy.mjs and test-cache.mjs. Serve only that folder with python3 -m http.server 8765 --bind 127.0.0.1 and open http://localhost:8765/index.html.

  1. 1. Step 1

    Run node test-cache.mjs against the unchanged supplied v1 practice files.

    You should see: 5 offline policy checks passed.

    Policy assertions, worker lifecycle observations, and offline browser reloads are separate evidence. Cached resources are not guaranteed permanent or a backup of user records.

  2. 2. Step 2

    Collect the selected entries, controller version, stopped-server reload, fallback, and v2 update records.

    You should see: Each performed browser test has expected and observed results.

    Policy assertions, worker lifecycle observations, and offline browser reloads are separate evidence. Cached resources are not guaranteed permanent or a backup of user records.

  3. 3. Step 3

    Return the final packet to one declared version; record whether v1 or v2 is included.

    You should see: Source and reported release agree.

    Policy assertions, worker lifecycle observations, and offline browser reloads are separate evidence. Cached resources are not guaranteed permanent or a backup of user records.

  4. 4. Step 4

    Unregister only this practice worker and remove only its caches after retaining evidence.

    You should see: An offline project with cleanup instructions and unverified checks clearly marked.

    Policy assertions, worker lifecycle observations, and offline browser reloads are separate evidence. Cached resources are not guaranteed permanent or a backup of user records.

Now change one thing

Only the five Node policy assertions ran. How many real offline reloads were verified?

Your work

What to finish

Deliver source, policy assertions, version evidence, performed browser tests, and scoped cleanup/limits.

Common mistake

Watch for this

Presenting policy-only tests as an executed browser offline release.

How can I tell I understand it?

Demonstrate the rule: Policy assertions, worker lifecycle observations, and offline browser reloads are separate evidence. Cached resources are not guaranteed permanent or a backup of user records. Use the supplied variant to distinguish a changed result from a broken implementation.

Try 3 questions

Quick knowledge check

Answer all 3 questions. Get at least 2 right and the lesson completes automatically.

Not yet passed

You’ll get an explanation for each answer. Signed in? Your results save to your account.

1What do the five offline policy checks establish?
2Why include the final declared cache version in the packet?
3Which limitation belongs in this offline project?
0 of 3 answeredApply the lesson to a short question, then review the explanation.
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Finish this lesson

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.

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Sources and further reading

Explore the references behind this lesson.

developer.mozilla.org — Service_Worker_API
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.

developer.mozilla.org — Cache
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.

developer.mozilla.org — Secure_Contexts
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.

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