Deep Clone II

Requirements

• Export deepClone as named and default. Copy graphs containing null, undefined, booleans, strings, numbers (including NaN and infinities), arrays, and ordinary/null-prototype objects with data properties. Return primitives unchanged.
• Preserve graph topology: every reachable source container has exactly one corresponding fresh clone within a call. Repeated references in the source must refer to the same cloned container. Self-cycles and mutual object/array cycles must terminate and point to cloned nodes, never original containers. This differs from Deep Clone, which duplicated repeated occurrences.
• Copy only own enumerable string-keyed properties. Preserve ordinary versus null object prototypes; preserve array length, sparse holes, indexed elements, and own enumerable custom string properties. Ignore non-enumerable and symbol-keyed properties.
• Safely copy special keys such as __proto__ and constructor as own data properties without prototype pollution. Cloned properties are writable, enumerable, and configurable even when input is frozen.
• Do not mutate input. Separate calls must return independent cloned graphs. Do not use JSON serialization, structuredClone, or a cloning library. Functions, symbol/BigInt values, Date, Map, Set, accessors, class instances, custom prototypes, and unbounded recursion depth are outside scope; validation is not required.

Examples

Input: const node={name:"root"}; node.self=node; const copy=deepClone(node); [copy!==node,copy.self===copy]
Output: [true,true]

Input: const shared={n:1}; const copy=deepClone({a:shared,b:shared}); [copy.a===copy.b,copy.a!==shared]
Output: [true,true]