Fix structuredClone Error in Svelte

structuredClone Errors in Svelte

The structuredClone() API provides deep copying of JavaScript objects, but it throws when encountering values that can't be cloned — functions, DOM nodes, or certain platform objects.

When This Error Appears

• Passing functions or class methods through structuredClone()
• Attempting to clone objects with Symbol properties
• Server components trying to serialize client-side objects
• State management libraries deep-cloning complex stores

The Solution

// Bad: structuredClone can't handle functions
const state = {
  count: 0,
  increment: () => state.count++,
};
const copy = structuredClone(state); // DataCloneError!

// Good: strip non-cloneable properties
const cloneState = (state) => {
  const { increment, ...data } = state;
  return structuredClone(data);
};

// Alternative: use JSON for simple cases
const copy = JSON.parse(JSON.stringify(data));

When to Use What

Pick the method that matches your data shape. For most state management needs, structuredClone works — just ensure you strip functions first.

Bugsly Tracks Clone Failures

[Bugsly](https://bugsly.io) shows you the exact object property that triggered the DataCloneError, with the full object structure for context — no more binary searching through nested state.