adding-frontend-feature

name	adding-frontend-feature
description	Add a new UI feature to the FoxESS dashboard frontend. Use when building dashboard components, adding panels, implementing settings toggles, or when asked to modify public/index.html.
user-invocable	true
argument-hint	[e.g. 'add battery health panel' or 'dark mode toggle']

Adding a Frontend Feature

You are adding a new feature to the FoxESS Battery Monitor dashboard. The entire frontend is a single file: public/index.html.

Before Starting

1. Read public/index.html to understand the current structure
2. Identify where the new feature fits (header, stats grid, weather panel, settings, etc.)
3. Plan the changes needed: HTML, CSS, and JS

iOS 12 Compatibility (MANDATORY)

All JavaScript in public/index.html MUST work on iOS 12 Safari:

• Use var — never let or const
• Use function() {} — never arrow functions () => {}
• Use string concatenation — never template literals
• Use indexed for loops — never for...of
• Use XMLHttpRequest — never fetch()
• No destructuring, spread, rest, optional chaining, nullish coalescing

Implementation Steps

1. Add HTML in the appropriate section of the file
2. Add CSS in the <style> block, following existing patterns:
   • Dark theme: background #1a1a2e, cards #16213e, text #e0e0e0
   • Accent colors: green #4ade80, blue #60a5fa, yellow #fbbf24
   • Use existing class naming conventions
3. Add JavaScript:
   • Cache new DOM elements in initializeElements() and add to the elements object
   • Store any user config in the config object (persisted to localStorage)
   • If adding a settings toggle, add it to the settings panel HTML, loadSettings(), and saveSettings()
   • If fetching external data, use XMLHttpRequest with onreadystatechange
   • If using Open-Meteo time data, use &timeformat=unixtime and new Date(timestamp * 1000)
4. Bump version: Update <meta name="app-version" content="X.Y.Z"> (semver)

Validation Checklist

Before finishing, grep for these patterns that would break iOS 12:

• Arrow functions: =>
• Let/const: \blet\b, \bconst\b (in JS, not CSS)
• Template literals: backtick characters
• For...of: for.*of

After Implementation

1. Ask the user if they want to commit and push
2. If committing, use a concise message with Co-Authored-By: Codex Opus 4.5 <[e-mail]>
3. Run /reflect to update documentation if the change is significant