ESON (or: yet another stab at slightly improving JSON)

example.eson.js

// ESON is like JSON.
// ESON files should use the `.eson` file extension and the `application/eson` MIME type.

// This is meant to be as close to JSON as possible (and backwards compatible), but having learned a few lessons.

{
  // It's backwards compatible with JSON.
  "key": "value",
    
  // Obviously, the big feature is it supports comments:
  /* 
    I removed comments from JSON because I saw people were using them to hold parsing directives, 
    a practice which would have destroyed interoperability. I know that the lack of comments makes 
    some people sad, but it shouldn't. 
    - Douglas Crockford, 2012
  */
  // The above concern is valid, and ESON is a little less interoperable. But a little nicer. Trade offs!
  // But it does mean you can use comments for parsing directives (or streaming hints) if you want.
  // Though there's a better way we'll talk about later.

  // It supports one new kind of string, stolen from ES. These are delimited with backticks.
  `key`: `value`,
    
  // This lets you use multiline strings:
  `like

this`: `which is a 
contrived
example
sorry`,
  
  // Or put single or double quotes inside:
  `single 'quotes'`: `and "double quotes"`,
  
  // It also supports unquoted keys, like ES.
  so_this_is: "totally fine",
    
  // And, to add insult to injury, like ES, the new backtick strings support tags.
  atag`on both the keys`: anothertag`and values`,
    
  // Parsers probably should just drop the tags by default, but you should be able to 
  // fish them out somehow to let applications provide data type hints.
  // But they can always fall back to JSON data types if they receive unknown tags.
  date: iso8601`2019-09-09T23:19:42+00:00`,
  id`user`: 645,
  
  // The only other difference is that trailing commas are allowed:
  numbers: [
    1,
    2,
    3,
  ],
}