Description
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:
objis a valid JSON object or array2 <= JSON.stringify(obj).length <= 105
Solutions
Solution 1
TypeScript
function undefinedToNull(obj: Record<any, any>): Record<any, any> { for (const key in obj) { if (typeof obj[key] === 'object') { obj[key] = undefinedToNull(obj[key]); } if (obj[key] === undefined) { obj[key] = null; } } return obj; } /** * undefinedToNull({"a": undefined, "b": 3}) // {"a": null, "b": 3} * undefinedToNull([undefined, undefined]) // [null, null] */(code-box)
