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JavaScriptBeginner#es6#strings
JavaScriptIntermediate#objects
What is the difference between shallow copy and deep copy?
A shallow copy duplicates the top level while nested references stay shared, so mutating a nested value affects both. A deep copy recursively duplicates everything.
Example
const a = { n: { v: 1 } };
const s = { ...a };
s.n.v = 9;
a.n.v; // 9 — shared
const d = structuredClone(a);