Read json file ignoring custom comments

Question

How can i read this file 'file.json':

# Comment01
# Comment02
{
   "name": "MyName"
}

and retrieve the json without comments?

I'm using this code:

var fs = require('fs');
var obj;
fs.readFile('./file.json', 'utf8', function (err, data) { 
  if (err) throw err;
  obj = JSON.parse(data);
});

it returns this error:

SyntaxError: Unexpected token # in JSON at position 0

Have npm some package to solve this question?

Hemã Vidal · Answer 1 · 2020-07-21T14:10:43.260

The perfect package for this problem is https://www.npmjs.com/package/hjson

hjsonText input:


{
  # hash style comments
  # (because it's just one character)

  // line style comments
  // (because it's like C/JavaScript/...)

  /* block style comments because
     it allows you to comment out a block */

  # Everything you do in comments,
  # stays in comments ;-}
}

Usage:

var Hjson = require('hjson');

var obj = Hjson.parse(hjsonText);
var text2 = Hjson.stringify(obj);

tarkh · Answer 2 · 2020-07-20T09:29:42.407

There is alternative package on NPM: json-easy-strip The main idea is to use just one-liner RegExp to strip all type of JS-style comments. And yes, it's simple and very possible! Package is more advanced, with some file caching etc, but still simple. Here is the core:

sweet.json

{
    /*
     * Sweet section
     */
    "fruit": "Watermelon", // Yes, watermelons is sweet!
    "dessert": /* Yummy! */ "Cheesecake",
    // And finally
    "drink": "Milkshake - /* strawberry */ or // chocolate!" // Mmm...
}

index.js

const fs = require('fs');
const data = (fs.readFileSync('./sweet.json')).toString();

// Striper core intelligent RegExp.
// The idea is to match data in quotes and
// group JS-type comments, which is not in
// quotes. Then return nothing if there is
// a group, else return matched data.
const json = JSON.parse(data.replace(/\\"|"(?:\\"|[^"])*"|(\/\/.*|\/\*[\s\S]*?\*\/)/g, (m, g) => g ? "" : m));

console.log(json);

//  {
//    fruit: 'Watermelon',
//    dessert: 'Cheesecake',
//    drink: 'Milkshake - /* strawberry */ or // chocolate!'
//  }

So now because you was asking about ShellScripting-style comments

#
# comments
#

We can extend our RegExp by adding \#.* at the end of it:

const json = JSON.parse(data.replace(/\\"|"(?:\\"|[^"])*"|(\/\/.*|\/\*[\s\S]*?\*\/|\#.*)/g, (m, g) => g ? "" : m));

Or, if you don't want JS-style comments at all:

const json = JSON.parse(data.replace(/\\"|"(?:\\"|[^"])*"|(\#.*)/g, (m, g) => g ? "" : m));

What does this pattern do if the comment has quotes in it? – Troy Apr 21 '23 at 15:45 — Troy, Apr 21 '23 at 15:45
It should cut all js-type comments, content doesn't matter. – tarkh Apr 23 '23 at 12:06 — tarkh, Apr 23 '23 at 12:06

peteb · Answer 3 · 2016-11-18T20:52:25.437

3

You can use your own RegExp pretty easily to match the comments beginning with a #

const matchHashComment = new RegExp(/(#.*)/, 'gi');
const fs = require('fs');

fs.readFile('./file.json', (err, data) => {
    // replaces all hash comments & trim the resulting string
    let json = data.toString('utf8').replace(matchHashComment, '').trim();  
    json = JSON.parse(json);
    console.log(json);
});

edited Nov 18 '16 at 20:52

answered Nov 18 '16 at 20:45

peteb

18,552
9
50
62

Yes it works, but i've adjusted the regex to: /#.*/ because if have just one # it not works. Thanks! – Hemã Vidal Nov 18 '16 at 20:51

score 2 · Answer 4 · answered Nov 18 '16 at 20:26

2

The package you are looking for is called strip-json-comments - https://github.com/sindresorhus/strip-json-comments

const json = '{/*rainbows*/"unicorn":"cake"}';

JSON.parse(stripJsonComments(json)); //=> {unicorn: 'cake'}

answered Nov 18 '16 at 20:26

Kalman

8,001
1
27
45

But in this package i can define my custom comment as #? – Hemã Vidal Nov 18 '16 at 20:35
Take a look at how that package deals with regular comments and it should give you an idea for dealing with custom comments – Kalman Nov 18 '16 at 20:46
I'd submitted an issue! https://github.com/sindresorhus/strip-json-comments/issues/31 to creator fix this solution in plugin. – Hemã Vidal Nov 18 '16 at 20:59
1

The author rejected my issue request, but suggested this package that works with "#" char as comment. https://www.npmjs.com/package/hjson – Hemã Vidal Nov 18 '16 at 22:00

score 2 · Accepted Answer · answered Jan 07 '23 at 15:11

2

let json = require('json5')
let fs = require('fs-extra')

let a = json.parse(fs.readFileSync("./tsconfig.json"))
console.log(a)

you can use json5 module

answered Jan 07 '23 at 15:11

PDHide

18,113
2
31
46

1

Widely used `30m` of weekly downloads. Looks perfect. And it allows single/multi line comments. – Hemã Vidal Jan 09 '23 at 11:52

score -3 · Answer 6 · answered Sep 14 '20 at 18:46

-3

Javascript has a comment remover built-in, no need for an extra package. I wouldn't do this for user input though.

eval(
  'var myjsonfile=' +
    require('fs')
      .readFileSync('./myjsonfile.json')
      .toString(),
);
console.log(myjsonfile);

answered Sep 14 '20 at 18:46

Robby Polana

9

Read json file ignoring custom comments

6 Answers6