Help & Resources

Symptom

Console shows: "Access blocked by CORS policy"

Cause

You're opening index.html directly as a file instead of through a local server.

Fix

Use a local server:

• VS Code: Install "Live Server" extension, right-click → Open with Live Server
• Python: python -m http.server 8000
• Node: npx http-server

Symptom

Insert/select returns { data: null, error: null } — no error but no data either!

Cause

Row Level Security is enabled but policies don't allow the operation.

Fix

1. Go to Supabase Dashboard → Authentication → Policies
2. Find your expenses table
3. Ensure policies exist for SELECT and INSERT
4. If missing, run the policy SQL from schema.sql

Symptom

Console shows: "supabaseConfig is not defined"

Cause

You haven't created your config.js file yet.

Fix

1. Find config.example.js in the project folder
2. Make a copy and rename it to config.js
3. Open config.js in your code editor
4. Replace YOUR_SUPABASE_PROJECT_URL with your actual URL
5. Replace YOUR_SUPABASE_ANON_KEY with your actual key
6. Save the file

Note: config.js is gitignored—it stays on your computer only and won't be pushed to GitHub.

Symptom

Dates show as 2024-01-15T08:00:00.000Z instead of "Jan 15, 2024"

Cause

The database returns dates in ISO format. You need to format them.

Fix

function formatDate(isoDate) {
  const date = new Date(isoDate + 'T00:00:00');
  return date.toLocaleDateString('en-US', {
    year: 'numeric',
    month: 'short',
    day: 'numeric'
  });
}

Symptom

When you submit the form, the page reloads and data may or may not save.

Cause

Default form behavior is to submit and reload. You need to prevent this.

Fix

Add event.preventDefault() as the first line in your submit handler:

form.addEventListener('submit', function(event) {
  event.preventDefault();
  // Handle form data with JavaScript
});

Symptom

supabase is not defined or supabase.from is not a function

Cause

The Supabase library isn't loaded, or scripts are in wrong order.

Fix

Ensure scripts load in this order in your HTML:

<script src="https://cdn.jsdelivr.net/npm/@supabase/supabase-js@2"></script>
<script src="config.js"></script>
<script src="app.js"></script>

And initialize with window.supabase.createClient()

Symptom

You pushed to GitHub, Vercel says "deployed", but site shows old content.

Fix

1. Hard refresh: Cmd+Shift+R (Mac) or Ctrl+Shift+R (Windows)
2. Check Vercel: Dashboard → Deployments → verify your commit deployed
3. Force redeploy: In Vercel, click "..." → "Redeploy"