Date Range Picker
Let users pick a valid date window without guessing which end comes first.
What it adds
A range picker with typed entry, clear boundary semantics, and no timezone drift between what was picked and what was stored.
What your agent is told to do
5
What your agent is told to do
5-
1
Support both calendar clicking and typed entry. Keyboard users should never be forced through a grid to enter two dates they already know.
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2
Decide and document whether the range is inclusive or exclusive at each end, and make the summary text say it in words.
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3
Handle reversed selection gracefully: picking the later date first should swap the endpoints, not reject the input.
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4
Treat a calendar date as a calendar date. Store and compare it without a time component, or you will ship the off-by-one-day bug where a user in UTC-8 picks the 1st and the server records the 31st.
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5
Do NOT reimplement locale formatting by hand. Use the platform's locale data for month names, date order, and first day of the week.
Edge cases it handles
6
Edge cases it handles
6- First day of week and date order differ by locale — read them from the locale, do not hardcode Sunday or MM/DD.
- Disabled dates inside a range must be enforced, not just greyed out.
- Minimum and maximum span limits must be explained when they block a selection.
- Open-ended ranges need explicit support and a clear label, not a blank endpoint.
- On mobile the calendar must fit without horizontal scroll and should not fight the native keyboard during typed entry.
- Presets like 'last 30 days' must state their boundary rule — whether today counts.
Definition of done
8
Definition of done
8- A range can be entered fully by keyboard and fully by pointer.
- Inclusive or exclusive boundaries are documented and reflected in the displayed summary.
- Selecting the end before the start produces a valid range.
- The stored range matches the dates the user saw, in every time zone.
- Locale determines date format and first day of week.
- Disabled dates and span limits are enforced with an explanation.
- 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.