The structured clone algorithm is an algorithm defined by the HTML5 specification for copying complex JavaScript objects. It is used internally when transferring data to and from Workers via postMessage()
or when storing objects with IndexedDB. It builds up a clone by recursing through the input object while maintaining a map of previously visited references in order to avoid infinitely traversing cycles.
Things that don't work with structured clone
Error
andFunction
objects cannot be duplicated by the structured clone algorithm; attempting to do so will throw aDATA_CLONE_ERR
exception.- Attempting to clone DOM nodes will likewise throw a
DATA_CLONE_ERR
exception. - Certain parameters of objects are not preserved:
- The
lastIndex
field ofRegExp
objects is not preserved. - Property descriptors, setters, and getters (as well as similar metadata-like features) are not duplicated. For example, if an object is marked read-only using a property descriptor, it will be read-write in the duplicate, since that's the default condition.
- The prototype chain does not get walked and duplicated.
- The
Supported types
Object type | Notes |
---|---|
All primitive types | However not symbols |
Boolean object | |
String object | |
Date | |
RegExp | The lastIndex field is not preserved. |
Blob |
|
File |
|
FileList |
|
ArrayBuffer | |
ArrayBufferView | This basically means all typed arrays like Int32Array etc. |
ImageData |
|
Array | |
Object | This just includes plain objects (e.g. from object literals) |
Map | |
Set |
See also
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