How to avoid invalid characters writing file using Jquery?

Question

I want to write the JSON value to a file and store to the user specified location, this operation will happen in client side.

I am working to create a file and to provide option to save the file.

 

Even though the JSON content  is filtered and only valid characters, once I write to a file I can find some invalid characters available in file.

 

Is anyone got same situation and resolved.

 

Thanks in advance.