How can I create a function to fix malformed JSON strings in JavaScript?

I’m working on a project where I need to handle JSON strings that are sometimes malformed. Specifically, I need a JavaScript function that can automatically repair these JSON strings and return them in a valid format.

For example, consider the following malformed JSON string:

const json = '{"key1":{"key2":"value1","key3":"value2"},"anotherkey":"va';

This string is missing a closing quote and a closing brace. The expected output should be:

{"key1":{"key2":"value1","key3":"value2"},"anotherkey":"va"}

I need a function, fixJson, that can handle various issues with malformed JSON, such as:

  • Missing closing braces or brackets
  • Unquoted keys or values
  • Incomplete strings

The function should return the corrected JSON string if possible or an error message if the JSON cannot be fixed.

Here’s what I’m looking for:

  1. A function that attempts to repair common issues with malformed JSON.
  2. It should ensure that the output is valid JSON and formatted correctly.
  3. If the JSON cannot be fixed, it should provide an informative error message.

Could you please help me with the implementation of such a function in JavaScript?

Thanks in advance!