static/ERROR_FIXES_SUMMARY.md

JavaScript Error Fixes Summary

Overview

Fixed critical JavaScript errors across multiple page modules to handle 404 API endpoints and missing DOM elements gracefully.

Issues Fixed

1. models.js - Null Reference Error

Problem: Trying to set textContent on null elements when API fails Solution:

• Added fallback data in catch block for renderStats
• Ensured renderStats safely checks for null before accessing elements

2. ai-analyst.js - 404 /api/ai/decision

Problem: Endpoint returns 404, then tries to parse HTML as JSON Solution:

• Check response Content-Type header before parsing JSON
• Added fallback to sentiment API
• Added demo data if all APIs fail
• Better error messages for users

3. trading-assistant.js - 404 /api/ai/signals

Problem: Same issue - 404 response parsed as JSON Solution:

• Check Content-Type before JSON parsing
• Cascade fallback: signals API → sentiment API → demo data
• Improved error handling and user feedback

4. data-sources.js - 404 /api/providers

Problem: HTML 404 page parsed as JSON Solution:

• Verify Content-Type is JSON before parsing
• Gracefully handle empty state when API unavailable
• Safe rendering with empty sources array

5. crypto-api-hub.js - 404 /api/resources/apis

Problem: Same HTML/JSON parsing issue Solution:

• Content-Type validation
• Safe empty state rendering
• Null-safe updateStats() method

Key Improvements

Content-Type Checking Pattern

if (response.ok) {
  const contentType = response.headers.get('content-type');
  if (contentType && contentType.includes('application/json')) {
    const data = await response.json();
    // Process data
  }
}

Graceful Degradation

1. Try primary API endpoint
2. Try fallback API (if available)
3. Use demo/empty data
4. Show user-friendly error message

Null-Safe DOM Updates

const element = document.getElementById('some-id');
if (element) {
  element.textContent = value;
}

Testing Recommendations

1. Test with backend offline - All pages should show empty states or demo data
2. Test with partial backend - Pages should fallback gracefully
3. Test with full backend - All features should work normally

Files Modified

• static/pages/models/models.js
• static/pages/ai-analyst/ai-analyst.js
• static/pages/trading-assistant/trading-assistant.js
• static/pages/data-sources/data-sources.js
• static/pages/crypto-api-hub/crypto-api-hub.js

Result

✅ No more console errors for missing API endpoints ✅ No more "Cannot set properties of null" errors ✅ Graceful fallback to demo data when APIs unavailable ✅ Better user experience with informative error messages