Implement a deep clone

Implement deepClone(value)

structuredClone exists natively now, but interviewers still ask for this, the point is testing whether you understand recursion over nested reference types, not whether you know the built-in exists.

Write deepClone(value) that returns a deep copy of a value made of plain objects, arrays, and primitives, mutating the clone must never affect the original, at any nesting depth.

const original = { nested: { count: 1 } };
const clone = deepClone(original);
clone.nested.count = 999;
original.nested.count; // still 1

Bonus (not tested here, but worth thinking about): how would you handle a value that contains a circular reference to itself?