===== ISTEM =====
Solve the following programming task.

TASK: Deep Clone an Object

Write a function 'deepClone(obj)' that deeply copies a given JavaScript object or array (including nested objects, arrays and primitives) without sharing references. It must also clone Date and RegExp objects.

STARTER CODE (javascript):
function deepClone(obj) {
  // Write your code here
}

module.exports = { deepClone };


RULES:
- Keep the function name and signature EXACTLY as given.
- Return working code only. No explanations.
- Put the code in a single ``` block.
- Try to solve it first. If you genuinely cannot, write only this single
  line instead of producing faulty code: CANNOT_SOLVE

===== HAM YANIT =====
```javascript
function deepClone(obj, map = new WeakMap()) {
  if (obj === null || typeof obj !== 'object') {
    return obj;
  }

  if (obj instanceof Date) {
    return new Date(obj.getTime());
  }

  if (obj instanceof RegExp) {
    return new RegExp(obj.source, obj.flags);
  }

  if (map.has(obj)) {
    return map.get(obj);
  }

  const copy = Array.isArray(obj) ? [] : {};
  map.set(obj, copy);

  for (const key of Object.keys(obj)) {
    copy[key] = deepClone(obj[key], map);
  }

  return copy;
}

module.exports = { deepClone };
```