structuredClone()

The global structuredClone() method creates a deep clone of a given value using the structured clone algorithm.

The method also allows transferable objects in the original value to be transferred rather than cloned to the new object. Transferred objects are detached from the original object and attached to the new object; they are no longer accessible in the original object.

value

The object to be cloned. This can be any structured-clonable type.

transfer Optional

An array of transferable objects in value that will be moved rather than cloned to the returned object.

The returned value is a deep copy of the original value.

DataCloneError DOMException

Thrown if any part of the input value is not serializable.

This function can be used to deep copy JavaScript values. It also supports circular references, as shown below:

// Create an object with a value and a circular reference to itself.
const original = { name: "MDN" };
original.itself = original;

// Clone it
const clone = structuredClone(original);

console.assert(clone !== original); // the objects are not the same (not same identity)
console.assert(clone.name === "MDN"); // they do have the same values
console.assert(clone.itself === clone); // and the circular reference is preserved

Transferable objects (only) can be transferred rather than duplicated in the cloned object, using the optional parameter's transfer value. Transferring makes the original object unusable.

The following code shows how to clone an array and transfer its underlying resources to the new object. On return, the original uInt8Array.buffer will be cleared.

var uInt8Array = new Uint8Array(1024 * 1024 * 16); // 16MB
for (var i = 0; i < uInt8Array.length; ++i) {
  uInt8Array[i] = i;
}

const transferred = structuredClone(uInt8Array, { transfer: [uInt8Array.buffer] });
console.log(uInt8Array.byteLength);  // 0

You can clone any number of objects and transfer any subset of those objects. For example, the code below would transfer arrayBuffer1 from the passed in value, but not arrayBuffer2.

const transferred = structuredClone(
   { x: { y: { z: arrayBuffer1, w: arrayBuffer2 } } },
   { transfer: [arrayBuffer1] });

• A polyfill of structuredClone is available in core-js
• Structured clone algorithm
• Structured clone polyfill