How to fix invalid input syntax for type uuid in PostgreSQL

ERROR: invalid input syntax for type uuid: ""
HINT: valid UUID values are of the form 'FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF'

// Wrong
const userId = "";
await db.query('INSERT INTO users (id, name) VALUES ($1, $2)', [userId, name]);

// Correct
const userId = null; // or undefined, depending on your ORM
await db.query('INSERT INTO users (id, name) VALUES ($1, $2)', [userId, name]);

# Wrong
User.objects.create(id="", name="John")

# Correct
User.objects.create(id=None, name="John")  # Let database generate UUID

// Wrong
User::create(['id' => '', 'name' => 'John']);

// Correct
User::create(['id' => null, 'name' => 'John']);

CREATE TABLE users (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  name TEXT NOT NULL
);

-- Wrong (treats it as a string literal)
id UUID DEFAULT 'uuid_generate_v4()'

-- Correct
id UUID DEFAULT uuid_generate_v4()

const { v4: uuidv4 } = require('uuid');
const newId = uuidv4(); // e.g., '9b1deb4d-3b7d-4bad-9bdd-2b0d7b3dcb6d'

import uuid
new_id = uuid.uuid4()  # Returns UUID object
new_id_str = str(uuid.uuid4())  # Returns string

function isValidUUID(str) {
  const uuidRegex = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i;
  return uuidRegex.test(str);
}

const userId = req.params.id;
if (!isValidUUID(userId)) {
  return res.status(400).json({ error: 'Invalid UUID format' });
}

-- Try casting and return NULL if invalid
CREATE OR REPLACE FUNCTION safe_uuid(text) RETURNS uuid AS $$
BEGIN
  RETURN $1::uuid;
EXCEPTION WHEN invalid_text_representation THEN
  RETURN NULL;
END;
$$ LANGUAGE plpgsql;

-- Usage
SELECT safe_uuid('invalid-uuid'); -- Returns NULL

-- Add new UUID column
ALTER TABLE users ADD COLUMN new_id UUID DEFAULT gen_random_uuid();

-- Copy data (creates new UUIDs; you can't convert bigint to meaningful UUIDs)
UPDATE users SET new_id = gen_random_uuid();

-- Drop old column and rename
ALTER TABLE users DROP COLUMN id;
ALTER TABLE users RENAME COLUMN new_id TO id;

-- Verify all values are valid UUIDs first
SELECT id FROM users WHERE id::text !~ '^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$';

-- If empty result, safe to convert
ALTER TABLE users ALTER COLUMN id TYPE UUID USING id::uuid;