The structured clone algorithm copies complex JavaScript objects. It is used internally when invoking structuredClone(), to transfer data between Workers via postMessage(), storing objects with IndexedDB, or copying objects for other APIs.

It clones by recursing through the input object while maintaining a map of previously visited references, to avoid infinitely traversing cycles.

• Function objects cannot be duplicated by the structured clone algorithm; attempting to throws a DataCloneError exception.
• Cloning DOM nodes likewise throws a DataCloneError exception.
• Certain object properties are not preserved:
  • The lastIndex property of RegExp objects is not preserved.
  • Property descriptors, setters, getters, and similar metadata-like features are not duplicated. For example, if an object is marked readonly with a property descriptor, it will be read/write in the duplicate, since that's the default.
  • The prototype chain is not walked or duplicated.

• HTML Specification: Safe passing of structured data
• Transferable objects
• structuredClone()
• window.history
• window.postMessage()
• Web Workers
• IndexedDB