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Course 277 · Digital course 40

Build Browser Saving with Export and Recovery

Build a fictional local reading-list app with versioned saved data, explicit browser-only wording, validated JSON export/import and corrupt-save recovery tests. Work from supplied original examples and check changed cases.

Before you start

Review Build your first website and the existing JavaScript course.

Add JavaScript Interactivity to a Web Page See everything you’ll need

Free download · Original practice data · No external account required. Download the starter pack

What you’ll leave with

A fictional local reading-list app with versioned saved data, explicit browser-only wording, validated JSON export/import and corrupt-save recovery tests.

Start course Start without an account. Sign in to save lesson progress across devices.

Your project

Start with the practice files. Build your project one lesson at a time.

Practice files are free without an account. Sign in to save your project record in My Proof: a description, checklist, and optional work link. Keep the original files in your own app or notebook; saving a project record does not upload them.

  1. Get your materialsDownload practice filesSupplied practice cases, a blank working record, complete lesson instructions, and annotated worked examples.
  2. Make your projectView the project checklist Work in your own notebook, document, or software. Use the supplied practice examples when you prefer.
  3. Keep a private recordSave a project record Sign in to save a description and checklist, then return to update them.
Course handbook

Know the route before you begin.

Here’s what you’ll need and what you’ll make. You can return to this guide during any lesson.

Who this is for

Learners ages 14+ and adults ready for the named prerequisite; no employment or private records required.

Prepare before lesson one
  • Review Build your first website and the existing JavaScript course.
  • Use a current browser, local text editor, Python 3 loopback file server, and optional Node.js for supplied logic assertions. No external packages or accounts required.
  • Use only invented titles in a fresh practice origin. Browser storage can be blocked or deleted.
Your final project

Finish with proof you can use.

A fictional local reading-list app with versioned saved data, explicit browser-only wording, validated JSON export/import and corrupt-save recovery tests.

Save a project record in My Proof
See project checklist and review criteria

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.
Three ideas to help you along the way
Three useful ideas

The rules behind the steps.

01

State the contract

Name inputs, permitted states and observable outputs before editing the implementation.

02

Preserve the evidence

Keep the actual source, changed input and expected/observed record so someone can repeat the work.

03

Test the boundary

Check a rejection or changed case and distinguish local practice from real service or native-tool behavior.

What do these words mean?
Key words

Key terms worth knowing.

origin
A scheme, host, and port combination.
schema
The allowed shape and types of stored data.
revision
A counter recorded with one saved envelope.
Blob
Browser representation of raw file-like data.
recovery
An explicit action after a failed or corrupt load.
Your route

6 lessons.
One useful project.

Work in order the first time. Each lesson makes something the next lesson can use.

  1. 1
    Up next

    Define the browser storage boundary

    Document the exact storage origin and distinguish reload persistence from account synchronization.

  2. 2
    29 min

    Save a versioned validated envelope

    Retain the validated envelope format and prove an invalid replacement leaves the earlier record intact.

  3. 3
    29 min

    Handle corrupt and unavailable saving

    Demonstrate a rejected corrupt load and a failed write without silently discarding prior data.

  4. 4
    29 min

    Export a portable explicit backup

    Create and inspect an actual JSON export and state its exact contents.

  5. 5
    29 min

    Import without trusting the file name

    Produce a valid/invalid import matrix proving rejected content retains the previous list.

  6. 6
    29 min

    Detect another tab and state the limits

    Deliver a two-tab observation or truthful unavailable note, alongside the validated backup/recovery project.

Use the tools

Tools to help you practice.

See all tools
ZIP · practice files

Build Browser Saving with Export and Recovery practice files

Supplied practice cases, a blank working record, complete lesson instructions, and annotated worked examples.

Text worksheet

Your course project worksheet

A downloadable text worksheet with each lesson’s working output, space for your answers, and the shared final-project checklist. Save your own copy.

Source transparency

Sources and further study.

Explore the references behind the lessons and take your learning further. Source notes explain access and reuse.

developer.mozilla.org — localStorage
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 — StorageEvent
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 — Blob
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.

Ready when you are

Start with the first useful move.

You’ll always know what to do, what to make, and where to go next.

Start lesson one