Are multi-line strings allowed in JSON?

JSON does not allow real line-breaks. You need to replace all the line breaks with \n.

eg:

"first line second line"

can saved with:

"first line\nsecond line"

Note:

for Python, this should be written as:

"first line\\nsecond line"

where \\ is for escaping the backslash, otherwise python will treat \n as the control character "new line"

Unfortunately many of the answers here address the question of how to put a newline character in the string data. The question is how to make the code look nicer by splitting the string value across multiple lines of code. (And even the answers that recognize this provide "solutions" that assume one is free to change the data representation, which in many cases one is not.)

And the worse news is, there is no good answer.

In many programming languages, even if they don't explicitly support splitting strings across lines, you can still use string concatenation to get the desired effect; and as long as the compiler isn't awful this is fine.

But json is not a programming language; it's just a data representation. You can't tell it to concatenate strings. Nor does its (fairly small) grammar include any facility for representing a string on multiple lines.

Short of devising a pre-processor of some kind (and I, for one, don't feel like effectively making up my own language to solve this issue), there isn't a general solution to this problem. IF you can change the data format, then you can substitute an array of strings. Otherwise, this is one of the numerous ways that json isn't designed for human-readability.

I have had to do this for a small Node.js project and found this work-around to store multiline strings as array of lines to make it more human-readable (at a cost of extra code to convert them to string later):

{
 "modify_head": [

  "<script type='text/javascript'>",
  "<!--",
  "  function drawSomeText(id) {",
  "  var pjs = Processing.getInstanceById(id);",
  "  var text = document.getElementById('inputtext').value;",
  "  pjs.drawText(text);}",
  "-->",
  "</script>"

 ],

 "modify_body": [

  "<input type='text' id='inputtext'></input>",
  "<button onclick=drawSomeText('ExampleCanvas')></button>"
 
 ],
}

Once parsed, I just use myData.modify_head.join('\n') or myData.modify_head.join(), depending upon whether I want a line break after each string or not.

This looks quite neat to me, apart from that I have to use double quotes everywhere. Though otherwise, I could, perhaps, use YAML, but that has other pitfalls and is not supported natively.

Check out the specification! The JSON grammar's char production can take the following values:

any-Unicode-character-except-"-or-\-or-control-character

\"

\\

\/

\b

\f

\n

\r

\t

\u four-hex-digits

Newlines are "control characters" so, no, you may not have a literal newline within your string. However you may encode it using whatever combination of \n and \r you require.

JSON doesn't allow breaking lines for readability.

Your best bet is to use an IDE that will line-wrap for you.

This is a really old question, but I came across this on a search and I think I know the source of your problem.

JSON does not allow "real" newlines in its data; it can only have escaped newlines. See the answer from @YOU. According to the question, it looks like you attempted to escape line breaks in Python two ways: by using the line continuation character ("\") or by using "\n" as an escape.

But keep in mind: if you are using a string in python, special escaped characters ("\t", "\n") are translated into REAL control characters! The "\n" will be replaced with the ASCII control character representing a newline character, which is precisely the character that is illegal in JSON. (As for the line continuation character, it simply takes the newline out.)

So what you need to do is to prevent Python from escaping characters. You can do this by using a raw string (put r in front of the string, as in r"abc\ndef", or by including an extra slash in front of the newline ("abc\\ndef").

Both of the above will, instead of replacing "\n" with the real newline ASCII control character, will leave "\n" as two literal characters, which then JSON can interpret as a newline escape.

Write property value as a array of strings. Like example given over here https://gun.io/blog/multi-line-strings-in-json/. This will help.

We can always use array of strings for multiline strings like following.

{
    "singleLine": "Some singleline String",
    "multiline": ["Line one", "line Two", "Line Three"]
} 

And we can easily iterate array to display content in multi line fashion.

While not standard, I found that some of the JSON libraries have options to support multiline Strings. I am saying this with the caveat, that this will hurt your interoperability.

However in the specific scenario I ran into, I needed to make a config file that was only ever used by one system readable and manageable by humans. And opted for this solution in the end.

Here is how this works out on Java with Jackson:

JsonMapper mapper = JsonMapper.builder()
   .enable(JsonReadFeature.ALLOW_UNESCAPED_CONTROL_CHARS)
   .build()

You can encode at client side and decode at server side. This will take care of \n and \t characters as well

e.g. I needed to send multiline xml through json

{
  "xml": "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"
}

then decode it on server side

public class XMLInput
{
        public string xml { get; set; }
        public string DecodeBase64()
        {
            var valueBytes = System.Convert.FromBase64String(this.xml);
            return Encoding.UTF8.GetString(valueBytes);
        }
}

public async Task<string> PublishXMLAsync([FromBody] XMLInput xmlInput)
{
     string data = xmlInput.DecodeBase64();
}

once decoded you'll get your original xml

<?xml version="1.0" encoding="utf-8" ?>
  <Structures>
       <inputs>
               # This program adds two numbers

               num1 = 1.5
               num2 = 6.3

               # Add two numbers
               sum = num1 + num2

               # Display the sum
               print('The sum of {0} and {1} is {2}'.format(num1, num2, sum))
       </inputs>
  </Structures>

If it's just for presentation in your editor you may use ` instead of " or '

const obj = {
myMultiLineString: `This is written in a \
multiline way. \
The backside of it is that you \
can't use indentation on every new \
line because is would be included in \
your string. \
The backslash after each line escapes the carriage return. 
`
}

Examples:

console.log(`First line \
Second line`);

will put in console: First line Second line

console.log(`First line 
second line`);

will put in console: First line second line

Hope this answered your question.

Try this, it also handles the single quote which is failed to parse by JSON.parse() method and also supports the UTF-8 character code.

    parseJSON = function() {
        var data = {};
        var reader = new FileReader();
        reader.onload = function() {
            try {
                data = JSON.parse(reader.result.replace(/'/g, "\""));
            } catch (ex) {
                console.log('error' + ex);
            }
        };
        reader.readAsText(fileSelector_test[0].files[0], 'utf-8');
}