How to add comments on JSON file

I don’t believe you can have an actual comment. The JSON should all be data, and if you include a comment, then it will be data too.

You could have a designated data element called "_comment" (or something) that would be ignored by apps that use the JSON data.

You would probably be better having the comment in the processes that generates/receives the JSON, as they are supposed to know what the JSON data will be in advance, or at least the structure of it.

But if you decided to:

{   "_comment": "comment text goes here...",   "glossary": {      "title": "example glossary",      "GlossDiv": {         "title": "S",         "GlossList": {            "GlossEntry": {               "ID": "SGML",               "SortAs": "SGML",               "GlossTerm": "Standard Generalized Markup Language",               "Acronym": "SGML",               "Abbrev": "ISO 8879:1986",               "GlossDef": {                  "para": "A meta-markup language, used to create markup languages such as DocBook.",                  "GlossSeeAlso": ["GML", "XML"]               },               "GlossSee": "markup"            }         }      }   }}