Webpack SyntaxError: Invalid left-hand side expression in postfix operation

I can see you're hitting a JavaScript syntax error in your sanity.js file - specifically "Invalid left-hand side expression in postfix operation" which typically means there's a syntax error like trying to use ++ or -- on something that isn't a variable, or having malformed code.

Don't give up! This is usually a quick fix once we spot the syntax error.

Most Likely Cause

Based on the error pointing to ./sanity.js at line 275, you likely have a syntax error in your Sanity configuration file. This often happens when:

1. Accidentally using incorrect syntax - Check your sanity.js (or sanity.config.js/ts) file around the line mentioned for things like:

   • Misplaced ++ or -- operators
   • Incorrect destructuring syntax
   • Missing commas or brackets
   • Copy-paste errors from tutorials

2. Module/import issues - The file might be trying to import or use something incorrectly

Steps to Fix

1. Check your sanity.js/sanity.config file for syntax errors:

// Look for syntax errors like:
something++ // on a non-variable
{ field++ } // invalid operation
await++ // invalid usage

2. If you just made changes, revert them temporarily:

• Use git to see what changed: git diff
• Revert to last working state: git checkout -- sanity.js (or the specific file)
• Or manually undo your recent changes

3. Delete .next folder and reinstall (clears build cache):

rmdir /s .next
del /s node_modules
npm install
npm run dev

4. Check your package.json dependencies: Make sure you have compatible versions. For a typical Next.js + Sanity setup, you should have something like:

{
  "next-sanity": "^5.x.x",
  "@sanity/client": "^6.x.x",
  "next": "^13.x.x or ^14.x.x"
}

Note: The swc warnings you're seeing (@next/swc-win32-x64-msvc warnings) are usually harmless - Next.js falls back to the wasm version, which works fine. The real issue is the syntax error.

Quick Fix to Try First

Since you mentioned you made changes:

1. Undo your recent changes to the sanity configuration
2. Delete the .next folder (this clears Next.js build cache)
3. Restart your dev server

If you can share the content of your sanity.js or sanity.config.js file (especially the area where you made changes), we can spot the exact syntax issue and help you fix it quickly!