Build a small notes app by asking an AI coding assistant to help with one feature at a time, then checking every change yourself. This tutorial outlines a browser-based app that can create, edit, delete, search, and save notes locally. It uses IndexedDB for structured browser storage and keeps accounts, cloud sync, and AI processing of note contents out of the first version.
What you will build
The first version needs only a note list, a simple editor, and clear feedback when a save succeeds or fails. Each note can use this example data model:
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- ID: a stable identifier so edits update the existing note rather than creating a duplicate.
- Title and body: the note’s editable text.
- Created and updated timestamps: useful for displaying or sorting notes.
This is a practical tutorial design, not a required standard. Keep the first release focused: no accounts, cross-device sync, rich-text editor, or AI summarization. Those features introduce additional implementation and privacy decisions.
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For a browser app whose notes should remain on the current device, IndexedDB is a reasonable choice for structured data. OWASP calls IndexedDB the current standard for structured client-side storage in its HTML5 Security Cheat Sheet. MDN explains that client-side storage can preserve state and support offline use, but available limits and persistence behavior vary with browsers and user settings; see MDN’s client-side storage guide.
#1 Best Overall
| Approach | What it provides | What it does not provide by itself |
|---|---|---|
| IndexedDB in the browser | Structured notes stored in the browser profile; suitable for local use and offline access when the app is available. | Automatic backup, cross-device sync, or protection from someone who can access the device or browser profile. |
| Account-backed cloud storage | A route to syncing notes between devices, depending on the service and implementation. | It is not a feature of browser storage alone; it requires decisions about accounts, authorization, transport security, and data handling. |
Choose local storage when the goal is a small, device-local app. If users need accounts or mobile storage for sensitive information, treat authentication, authorization, secure credential handling, and protected transport as separate requirements. OWASP’s Mobile Application Security Cheat Sheet recommends HTTPS, minimizing personal data, and obtaining consent before collecting or using it; for sensitive mobile data it also advises platform protections.
Use the coding assistant in small, reviewable steps
An AI coding assistant can help scaffold a project, implement a feature, and review code, but generated changes still need human inspection and testing. OpenAI describes Codex as an agent for writing, reviewing, and shipping code in its Codex learning resources. Access, plan eligibility, and workspace controls can vary; check the current Codex plan and availability information for your account and work environment.
- Give it relevant context. Identify the project’s framework, entry points, existing data layer, and any conventions visible in the repository. Avoid pasting secrets or unrelated files.
- Request one bounded change. For example: “Add a note list and an editor with title and body fields. Do not add authentication or cloud sync. Describe the files you change and the behavior I should verify.”
- Inspect the proposed diff. Check that the assistant changed only the expected files, that notes have stable IDs, and that rendering and saving work as described.
- Ask about assumptions and checks. Ask it to identify edge cases—such as editing an existing note or handling a failed save—and to add appropriate tests where the project supports them.
- Run the project’s checks. Use the test, lint, or build commands already defined by the project, then try the app yourself in the browser. Do not treat an explanation or passing generated tests as proof that the feature behaves correctly.
OpenAI’s account of running Codex safely describes controls and governance for coding agents; the controls available to you depend on the product surface and configuration.
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1. Create a note
Ask the assistant to add a “New note” action that creates a note with a stable ID and timestamps, then opens it in the editor. Decide what happens to a blank note—for example, whether it is saved immediately or only after the user enters text—and make that behavior explicit. Verify that creating one note adds one list item and that selecting it opens the corresponding content.
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2. Edit and save
Have the editor update the selected note rather than inserting a new record. Save to IndexedDB and show a visible status such as “Saving…”, “Saved”, or “Could not save.” A success message should appear only after the storage operation succeeds; on failure, keep the text available in the editor and give the user a clear retry path. Test that changing a note’s title or body survives a page reload.
3. Delete a note
Add a delete action for the selected note. If deletion is immediate, provide a confirmation or an undo opportunity appropriate to the app. Verify that the note disappears from the list and is removed from storage, then reload to confirm it does not return.
4. Find a note
Start with a simple search that filters notes by title and body. Decide whether matching is case-insensitive and whether the list updates as the user types. Test a matching phrase, a non-matching phrase, and an empty search. Avoid adding full-text indexing or advanced query behavior until the basic workflow is reliable.
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Browser storage is not a confidentiality boundary. Scripts running in the page can access stored data, and a person with access to the local device or browser profile may be able to read or modify it. OWASP also warns that cross-site scripting can expose or alter browser-stored data. Render saved text as text rather than interpreting it as HTML, and keep session identifiers, credentials, and other secrets out of IndexedDB and local storage. See the OWASP HTML5 Security Cheat Sheet.
Local persistence should not be described as backup or sync. Users may lose local data, and browser storage limits and behavior depend on browser and user settings. If the app later adds an AI feature that processes note text, make the data flow clear before the user invokes it: what text is sent, to which service, and when. Keep the feature optional rather than silently forwarding private notes. No particular AI provider’s API terms are established here, so evaluate those terms before choosing a service.
Quick Recap
Check the finished first version
- Create a note, edit it, reload the app, and confirm the saved version appears.
- Confirm the interface distinguishes a successful save from a failed one.
- Delete a note and confirm it stays deleted after reload.
- Search by title and body, including a query with no matches.
- Check that note text is rendered as text and that no credentials or session identifiers are stored with notes.
- Describe storage honestly: notes are stored in this browser profile, not automatically backed up or synced to another device.
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