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    eon: EcmaScript Serialized Object Notation

    eon is a format for storing information, that is like JSON in every way, except that it supports comments.

    It was created because people use JSON for human-edited configuration files, and human-edited configuration files should support comments.

    The format is the same as JSON's, according to the JSON specification, except that single line (// comment) and multiline (/* comment */) comments, as specified by the EcmaScript specification, are ignored.

    This node.js package includes a parser based on Zach Carter's JSON parser in his JSON Lint module, which uses jison. jison is needed to build the the parser but not at runtime.


    You can install eon from npm.

    Command Line

    To convert a file from eon to json, run:

    npm install -g eon
    eon package.eon

    This will write package.json (overwriting it if it exists).


    require('./eon')('{/* hi */"x":3}')


    You're changing JSON! JSON was never supposed to change!

    No I'm not. I don't condone using the .json extension or the application/json content type. Instead use .eon and application/eon. This isn't a JSON dialect. This accepts a superset of JSON.

    Why not add support for single quoted strings, or unquoted object keys?

    I like the simplicity of JSON. I don't even mind that JSON disallows comments, when it is being used purely as a serialization format. The addition of comments is all I need to make JSON palatable for configuration files.

    Why not just use YAML?

    JSON, and eon, are more lightweight, and more people understand JSON than YAML.

    Why support both comment syntaxes, when JSON only supports one style of string quotes?

    I prefer to use the single-line comment syntax most of the time, but sometimes JSON is restricted to one object per line, in log files. This might happen with eon, too. If there is one object per line, the multiline syntax might be handy for commenting part of a complex expresssion.

    What about other languages?

    They're on the way! But in the meantime you can use the node.js command-line utility to convert to JSON first.


    Initial version implemented.


    Thank you:

    • Douglas Crockford for creating JSON
    • Kyle Simpson for passionately arguing for comment support
    • Aseem Kishore for creating json5, which inspired me to start working on this problem again
    • Zack Carter for creating jison and jsonlint


    Copyright 2012 Ben Atkin. Released under the terms of the MIT License.

    Copyright 2012 Zach Carter. Released under the terms of the MIT License.




    npm i eon

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