JavaScript Interview Question #148

What is structuredClone()?

Generators, Browser Storage, Security & Advanced Runtime Concepts Senior Advanced

Quick Interview Answer

structuredClone creates a deep clone of values supported by the structured clone algorithm. It can handle many values that JSON serialization does not preserve correctly, including circular references, Map, Set, Date, and various typed data structures.

Detailed Explanation

It does not clone every possible JavaScript value; for example, functions cannot be cloned with structuredClone. Developers should still understand the supported types and whether cloning is actually necessary for the design.

Code Example

const original = {
    created: new Date(),
    tags: new Set(["js", "web"])
};

original.self = original;

const copy = structuredClone(original);

console.log(copy !== original); // true
console.log(copy.created instanceof Date); // true
console.log(copy.self === copy); // true