"hello world" -> "hello world"

Strings clone exactly.

42.5 -> 42.5

Numbers clone exactly.

NaN -> NaN

NaN survives (JSON would turn it into null).

null -> null

Infinity survives (JSON would turn it into null).

0 -> 0

Negative zero is preserved.

12345678901234567890n -> 12345678901234567890n

BigInts clone (JSON throws on them).

true -> true

Booleans clone exactly.

null -> null

null clones exactly.

undefined -> undefined

undefined clones exactly.

Date(2026-01-15T10:30:00.000Z) -> Date(2026-01-15T10:30:00.000Z)

Dates clone as real Date objects, not strings.

/icon-[a-z]+/gi -> /icon-[a-z]+/gi

Source, flags and lastIndex are preserved.

Map(2) -> Map(2)

Maps clone with entries intact (JSON gives {}).

Set(3) -> Set(3)

Sets clone with values intact (JSON gives {}).

[1,"two",[3]] -> [1,"two",[3]]

Arrays deep-clone.

{"a":1,"b":{"c":[2,3]}} -> {"a":1,"b":{"c":[2,3]}}

Plain objects deep-clone.

{"d":"1970-01-01T00:00:00.000Z","m":{},"u":{"0":9}} -> {"d":"1970-01-01T00:00:00.000Z","m":{},"u":{"0":9}}

Nested special types all survive together.

Uint8Array(3 bytes) -> Uint8Array(3 bytes)

Typed arrays keep their type and bytes.

Float64Array(16 bytes) -> Float64Array(16 bytes)

Typed arrays keep their type and values.

ArrayBuffer(4) -> ArrayBuffer(4)

Raw buffers clone byte for byte.

DataView(8 bytes) -> DataView(8 bytes)

DataViews clone with their bytes.

Blob(5 bytes, "text/plain") -> Blob(5 bytes, "text/plain")

Blobs clone (bytes included), useful for file pipelines.

Blob(4 bytes, "text/plain")

Files keep name, type and size.

Error: boom -> Error: boom

Message and extra props survive, but the stack is regenerated and the subclass is lost.

NotFoundError: not here -> NotFoundError: not here

DOMExceptions clone with name and message intact.

function () {...}

Functions are not serializable and throw DataCloneError.

Symbol(id)

Symbols are not serializable and throw DataCloneError.

{"x":3,"y":4} -> {"x":3,"y":4}

Own properties survive, but the prototype is dropped, so methods like dist() are lost.

[circular] -> [circular]

Circular graphs clone correctly (JSON throws on them).