Conditional Form Fields
Show only the fields that matter based on what the user already answered.
What it adds
Form fields that appear, disappear, and become required depending on other answers, with the server agreeing about which branch is live.
What your agent is told to do
5
What your agent is told to do
5-
1
Find the forms with fields that only apply in some cases and define, per field, the exact condition that shows it.
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2
Write down one explicit rule for hidden values: cleared, preserved, or ignored. Apply it consistently — silent submission of a value the user can no longer see is the classic bug here.
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3
Make 'required' conditional too. A hidden field must never block submission, and a revealed field must be validated.
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4
Mirror the same branch logic on the server. The client decides what to show; the server decides what is valid.
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5
Do NOT use display:none alone to hide a field. A visually hidden input is still focusable, still submitted, and still read by screen readers — remove it or disable it properly.
Edge cases it handles
6
Edge cases it handles
6- Editing an existing record must reopen the branch that record was saved with, including nested conditions.
- Revealed fields must be announced to assistive technology without yanking focus away from the control the user just used.
- A chain of conditions must collapse cleanly — hiding a parent must hide and resolve everything under it.
- Layout must not jump when a field appears; reserve space or animate the height.
- A server validation error on a hidden field must reopen the branch containing it rather than showing an error nobody can find.
- Autosave and draft restore must record which branch was active, not just the field values.
Definition of done
8
Definition of done
8- Each conditional field has a stated rule for what happens to its value when hidden.
- Hidden fields are never submitted, never required, and never focusable.
- The server applies the same branch logic as the client.
- Editing an existing record restores the correct branch.
- Newly revealed fields are announced and do not steal focus.
- Errors on fields inside a collapsed branch reveal that branch.
- The feature matches the existing design system.
- No existing functionality is broken.
Related features
Unit Converter
Unit Converter
Let people convert a value between units without leaving the page they are on.
What it does
An inline converter that takes a typed value in one unit and shows the equivalent in another, in place.
How it works
- 1 Start from the units the app actually deals in. A shipping tool needs weight and length; a recipe tool needs volume and temperature. Ship those and leave the rest out.
- 2 Convert as the user types, with the result visible beside the input rather than behind a submit button. Let either side be edited so the conversion runs in both directions.
- 3 Reuse the app's existing number parsing and display formatting rather than writing new ones. If Locale-Aware Numbers and Dates or Number Formatting Component is already present, the converter must render through it so grouping and decimal marks match the rest of the app.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/unit-converter
Voice Dictation
Voice Dictation
Put a microphone in text fields so people can speak their input instead of typing it.
What it does
A dictation control on the app's longer text inputs that transcribes speech into the field as the user talks.
How it works
- 1 Add the control to the fields where typing is genuinely tedious: long descriptions, notes, comments, and message bodies. A microphone on a postcode field is clutter.
- 2 Show interim results in the field as they arrive, visually distinct from committed text, so the speaker can see it is working and correct course before they finish.
- 3 Reuse the app's existing Voice Transcription for the server-side path so one recognition configuration and one set of language settings serve both dictation and recorded audio.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/voice-dictation
Code Editor Field
Code Editor Field
Edit code, JSON, and config with syntax highlighting instead of a bare textarea.
What it does
A form field backed by a real code editor: syntax highlighting, a language mode per field, and inline validation that tolerates work in progress.
How it works
- 1 Load the editor library lazily, only on views that use it, and render a usable plain textarea until it arrives. It must never block first paint.
- 2 Set the language mode per field from what the field actually holds, and validate against that mode.
- 3 Report syntax errors as you go, but never block typing or reset the content. Half-written JSON is a normal intermediate state; only submission should be gated.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/code-editor-field
How it works
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1
Copy the link
Grab the Markdown instruction URL for this feature.
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2
Give it to your AI
Paste it into Claude Code, Cursor, v0, Lovable — whatever you build with.
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3
It inspects, then implements
Your agent reads your existing app first, then adds the feature to fit it.
Works with your stack
These instructions are written to adapt. They tell the agent to detect your framework, match your existing design system, and reuse what you already have — rather than assuming a particular stack.
Need it tighter than that? Customize the feature and tell it exactly what you're running.