methods for removing json comments using javascript

Question

methods for removing json comments using javascript

Looking to remove JSON comments using JavaScript? I believe a regular expression would be the most efficient method.

{
    "field": { // comments
         "n": 1 /* multi-line ...
                                 comments */
    },
    "field2": " // comments in string , /* here */ "
}

This should be effective for the provided example.
Note: comments within strings should not be deleted.

Update: I understand that comments in JSON are not standard, but for simplicity, I want to include them and then remove them. Many tools can handle parsing JSON with comments.

Update 2: The example above is actually a string, I failed to mention that (apologies), and I see some responses assuming it is JavaScript code.

Update 3: I once again forgot to enclose key names in double quotes, the question has been updated.

javascript json regex

Answer 1

Answer №1

While leaving comments in JSON may not be common practice, there are situations where it can be beneficial. I created a small nodejs package specifically for this purpose: json-easy-strip

Your JSON file can include any valid JavaScript comments:

{
    /*
     * Delicious section
     */
    "fruit": "Watermelon", // Yes, watermelons are delicious!
    "dessert": /* Yummy! */ "Cheesecake",
    // And lastly
    "drink": "Milkshake - /* strawberry */ or // chocolate!" // Mmm...
}

Here is how the comments can be stripped:

//
// Our JSON string
let jsonString = `{
    /*
     * Delicious section
     */
    "fruit": "Watermelon", // Yes, watermelons are delicious!
    "dessert": /* Yummy! */ "Cheesecake",
    // And lastly
    "drink": "Milkshake - /* strawberry */ or // chocolate!" // Mmm...
}`;

//
// One-liner comment remover
jsonString = jsonString.replace(/\\"|"(?:\\"|[^"])*"|(\/\/.*|\/\*[\s\S]*?\*\/)/g, (m, g) => g ? "" : m);

//
// Parse jsonString and display the result
console.log(JSON.parse(jsonString));

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

Answer 2

While leaving comments in JSON may not be common practice, there are situations where it can be beneficial. I created a small nodejs package specifically for this purpose: json-easy-strip

Your JSON file can include any valid JavaScript comments:

{
    /*
     * Delicious section
     */
    "fruit": "Watermelon", // Yes, watermelons are delicious!
    "dessert": /* Yummy! */ "Cheesecake",
    // And lastly
    "drink": "Milkshake - /* strawberry */ or // chocolate!" // Mmm...
}

Here is how the comments can be stripped:

//
// Our JSON string
let jsonString = `{
    /*
     * Delicious section
     */
    "fruit": "Watermelon", // Yes, watermelons are delicious!
    "dessert": /* Yummy! */ "Cheesecake",
    // And lastly
    "drink": "Milkshake - /* strawberry */ or // chocolate!" // Mmm...
}`;

//
// One-liner comment remover
jsonString = jsonString.replace(/\\"|"(?:\\"|[^"])*"|(\/\/.*|\/\*[\s\S]*?\*\/)/g, (m, g) => g ? "" : m);

//
// Parse jsonString and display the result
console.log(JSON.parse(jsonString));

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

Answer 3

Answer №2

A quick and efficient method involves using JSON.stringify followed by JSON.parse to easily clean up the data.

Answer 4

A quick and efficient method involves using JSON.stringify followed by JSON.parse to easily clean up the data.

Answer 5

Answer №3

Utilize the javascript parser to handle it:

a = {
    filed: { // comments
         n: 1 /* multi-line ...
                                 comments */
    },
    field2: " // comments in string , /* here */ "
}
a.toSource()
/*
({filed:{n:1}, field2:" // comments in string , /* here */ "})
*/

You have the option to achieve the same outcome with a string (based on the edited question) in a similar manner:

a =   'a = {\r\n  filed: { // comments  n: 1 \r\n/* multi-line ...  comments */\r\n},\r\n'
    + 'field2: " // comments in string , /* here */ "\r\n}'
eval(a).toSource().toString();

However, it appears that this method does not function with chrome. Oh, I overlooked, it is specifically for FF, my apologies (in Javascript version 3).

I discovered an alternative at https://gist.github.com/archan937/1961799 so the following will function in most other browsers as well.

function inspect(object) {
  switch (typeof(object)) {
  case "undefined":
    return "undefined";
  case "string":
    return "\"" + object.replace(/\n/g, "\\n").replace(/\"/g, "\\\"") + "\"";
  case "object":
    if (object == null) {
      return "null";
    }
    var a = [];
    if (object instanceof Array) {
      for (var i in object) {
        a.push(inspect(object[i]));
      };
      return "[" + a.join(", ") + "]";
    } else {
      for (var key in object) {
        if (object.hasOwnProperty(key)) {
          a.push(key + ": " + inspect(object[key]));
        }
      };
      return "{" + a.join(", ") + "}";
    }
  default:
    return object.toString();
  }
};

a = 'a = {\r\n  filed: { // comments  n: 1 \r\n/* multi-line ...  comments */\r\n},\r\n'
    + 'field2: " // comments in string , /* here */ "\r\n}'

alert(inspect(eval(a)));

Answer 6

Utilize the javascript parser to handle it:

a = {
    filed: { // comments
         n: 1 /* multi-line ...
                                 comments */
    },
    field2: " // comments in string , /* here */ "
}
a.toSource()
/*
({filed:{n:1}, field2:" // comments in string , /* here */ "})
*/

You have the option to achieve the same outcome with a string (based on the edited question) in a similar manner:

a =   'a = {\r\n  filed: { // comments  n: 1 \r\n/* multi-line ...  comments */\r\n},\r\n'
    + 'field2: " // comments in string , /* here */ "\r\n}'
eval(a).toSource().toString();

However, it appears that this method does not function with chrome. Oh, I overlooked, it is specifically for FF, my apologies (in Javascript version 3).

I discovered an alternative at https://gist.github.com/archan937/1961799 so the following will function in most other browsers as well.

function inspect(object) {
  switch (typeof(object)) {
  case "undefined":
    return "undefined";
  case "string":
    return "\"" + object.replace(/\n/g, "\\n").replace(/\"/g, "\\\"") + "\"";
  case "object":
    if (object == null) {
      return "null";
    }
    var a = [];
    if (object instanceof Array) {
      for (var i in object) {
        a.push(inspect(object[i]));
      };
      return "[" + a.join(", ") + "]";
    } else {
      for (var key in object) {
        if (object.hasOwnProperty(key)) {
          a.push(key + ": " + inspect(object[key]));
        }
      };
      return "{" + a.join(", ") + "}";
    }
  default:
    return object.toString();
  }
};

a = 'a = {\r\n  filed: { // comments  n: 1 \r\n/* multi-line ...  comments */\r\n},\r\n'
    + 'field2: " // comments in string , /* here */ "\r\n}'

alert(inspect(eval(a)));

Answer 7

Answer №4

If you're looking to eliminate comments, especially in JSON5 format, you should check out the decomment library available at this link.

This powerful tool can effectively remove comments from JSON5, JavaScript ES6, CSS, and even HTML with ease.

const decomment = require('decomment');

const exampleCode = "let x; // a comment";

decomment(exampleCode); //=> let x;

Answer 8

If you're looking to eliminate comments, especially in JSON5 format, you should check out the decomment library available at this link.

This powerful tool can effectively remove comments from JSON5, JavaScript ES6, CSS, and even HTML with ease.

const decomment = require('decomment');

const exampleCode = "let x; // a comment";

decomment(exampleCode); //=> let x;

Answer 9

Answer №5

Here's my take on it: if you're considering keeping an invalid JSON file with comments for production purposes, that's your call. However, deploying such a file on your live website and then resorting to JavaScript workarounds to make it function properly isn't the best look. I suggest creating a clean JSON file for deployment and keeping the commented code for your eyes only. The end user doesn't need to see it, and unnecessary indenting spaces only add to the data transfer size.

If you're looking to remove those comments, here's one approach:

var invalidJSON = "{\n\"filed\": { // comments\n\"n\": 1 /* multi-line ...\ncomments */\n},\n\"field2\": \" // comments in string , /* here */ \"\n}";

eval("var result = " + invalidJSON);
var result = JSON.stringify(result);
alert(result); // The result should be a valid JSON object

Alternatively, you can treat it as JavaScript instead of JSON with a few modifications to the file:

// file.js
var data = {
    "filed": { // comments
         "n": 1 /* multi-line ...
                                 comments */
    },
    "field2": " // comments in string , /* here */ "
};

In your HTML page:

<script type="text/javascript" src="file.js"></script>

This will import the object to your page under the name data.

Answer 10

Here's my take on it: if you're considering keeping an invalid JSON file with comments for production purposes, that's your call. However, deploying such a file on your live website and then resorting to JavaScript workarounds to make it function properly isn't the best look. I suggest creating a clean JSON file for deployment and keeping the commented code for your eyes only. The end user doesn't need to see it, and unnecessary indenting spaces only add to the data transfer size.

If you're looking to remove those comments, here's one approach:

var invalidJSON = "{\n\"filed\": { // comments\n\"n\": 1 /* multi-line ...\ncomments */\n},\n\"field2\": \" // comments in string , /* here */ \"\n}";

eval("var result = " + invalidJSON);
var result = JSON.stringify(result);
alert(result); // The result should be a valid JSON object

Alternatively, you can treat it as JavaScript instead of JSON with a few modifications to the file:

// file.js
var data = {
    "filed": { // comments
         "n": 1 /* multi-line ...
                                 comments */
    },
    "field2": " // comments in string , /* here */ "
};

In your HTML page:

<script type="text/javascript" src="file.js"></script>

This will import the object to your page under the name data.

Answer 11

Answer №6

Many responses suggest using eval, but I caution against it. While it may appear harmless, using eval can introduce risks. Instead, I recommend avoiding eval, even for simple tasks like this.

Here is my modified version of Havenard's solution, which employs a similar yet safer approach.

var invalid_json = "{\n\"filed\": { // comments\n\"n\": 1 /* multi-line ...\ncomments */\n},\n\"field2\": \" // comments in string , /* here */ \"\n}";

var json = (new Function("return " + invalid_json))();
var x = JSON.stringify(json);
alert(x); // x should be valid JSON of that

Answer 12

Many responses suggest using eval, but I caution against it. While it may appear harmless, using eval can introduce risks. Instead, I recommend avoiding eval, even for simple tasks like this.

Here is my modified version of Havenard's solution, which employs a similar yet safer approach.

var invalid_json = "{\n\"filed\": { // comments\n\"n\": 1 /* multi-line ...\ncomments */\n},\n\"field2\": \" // comments in string , /* here */ \"\n}";

var json = (new Function("return " + invalid_json))();
var x = JSON.stringify(json);
alert(x); // x should be valid JSON of that

methods for removing json comments using javascript

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

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