Behavior of [Structured Clone]

Structured clone is JavaScript’s algorithm to create “deep copies” of values. It is used for postMessage() and therefore is used extensively under the hood with Comlink. By default, every function parameter and function return value is structured cloned. Here is a table of how the structured clone algorithm handles different kinds of values. Or to phrase it differently: If you pass a value from the left side as a parameter into a proxy’d function, the actual function code will get what is listed on the right side.

Input	Output	Notes
[1,2,3]	[1,2,3]	Full copy
{a: 1, b: 2}	{a: 1, b: 2}	Full copy
{a: 1, b() { return 2; }	{a: 1}	Full copy, functions omitted
new MyClass()	{...}	Just the properties
Map	Map	Map is structured cloneable
Set	Set	Set is structured cloneable
ArrayBuffer	ArrayBuffer	ArrayBuffer is structured cloneable
Uint32Array	Uint32Array	Uint32Array and all the other typed arrays are structured cloneable
Event	❌
Any DOM element	❌
MessagePort	❌	Only transferable, not structured cloneable
Request	❌
Response	❌
ReadableStream	❌	Streams are planned to be transferable, but not structured cloneable