Given a deeply nested object or array obj, return the object obj with any undefined values replaced by null.

undefined values are handled differently than null values when objects are converted to a JSON string using JSON.stringify(). This function helps ensure serialized data is free of unexpected errors.

 

Example 1:

Input: obj = {"a": undefined, "b": 3}
Output: {"a": null, "b": 3}
Explanation: The value for obj.a has been changed from undefined to null

Example 2:

Input: obj = {"a": undefined, "b": ["a", undefined]}
Output: {"a": null,"b": ["a", null]}
Explanation: The values for obj.a and obj.b[1] have been changed from undefined to null

 

Constraints:

• obj is a valid JSON object or array
• 2 <= JSON.stringify(obj).length <= 105