Adding comma separators to otherwise valid JSON string

Question

I have a JSON-like string read from many files that have JSON-like syntax without commas separating the root key-value pairs (e.g. "name": "Apple Beery" instead of "name": "Apple Beery",):

var data = `{
    "name": "Apple Beery"
    "phrases": [
        "a",
        "b",
        "It's"
    ]
    "reference": 19
    "friends": [
        {
            "name": "Dog",
            "reference": 14
        },
        {
            "name": "Markus Beery",
            "reference": 30
        }
    ]
    "last": "b"
}`;

Is there way to add dynamically commas back to the JSON string, so the JSON can be parsed like this:

var data = JSON.parse(`{
    "name": "Apple Beery",
    "phrases": [
        "a",
        "b",
        "It's"
    ],
    "reference": 19,
    "friends": [
        {
            "name": "George Beery",
            "reference": 14
        },
        {
            "name": "Markus Beery",
            "reference": 30
        }
    ],
    "last": "b"
}`);

The first JSON string is not valid AFAIK, and it would take a full parser to bring it up to snuff to be parsed later by a JSON parser. What is the source of that JSON string? I think you should fix the problem at its source. — Tim Biegeleisen
– Tim Biegeleisen, Commented Jan 1, 2019 at 2:23
The first JSON string is just missing the commas. These strings come from YAML config files that were written with valid JSON, except for the commas. I want to move everything to the proper JSON format. — Kwoppy
– Kwoppy, Commented Jan 1, 2019 at 2:26
Can you explain what you mean by "These strings come from YAML config files that were written with valid JSON, except for the commas."? Because YAML can be parsed and dumped to JSON. So, maybe you're going about this all wrong. — Nate
– Nate, Commented Jan 1, 2019 at 3:28

CertainPerformance · Accepted Answer · 2019-01-01 02:27:32Z

1

You can use a regular expression to match the last character in a line (anything but a comma, {, or [) and, if the next line starts with a {, [, or ", replace with that character plus a comma. If there may be digits on the next line, add \d into the final character set too:

const data = `{
    "name": "Apple Beery"
    "phrases": [
        "a",
        "b",
        "It's"
    ]
    "reference": 19
    "friends": [
        {
            "name": "Dog",
            "reference": 14
        },
        {
            "name": "Markus Beery",
            "reference": 30
        }
    ]
    "last": "b"
}`;
const json = data.replace(/[^,{[](?=\n *["[{\d])/gm, '$&,');
console.log(JSON.parse(json));

The pattern

[^,{[](?=\n *["[{\d])

means:

[^,{[] - Any character that isn't a comma, a {, or [
(?=\n *["[{\d]) - Lookahead for:
- \n * - A newline character, followed by any number of spaces, and
- ["[{\d] - any character but a [, {, or digit

answered Jan 1, 2019 at 2:27

CertainPerformance

373k55 gold badges354 silver badges359 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Tim Biegeleisen Over a year ago

Good answer, but I fear that it might break if the actual JSON input could happen to be all on a single line.

Collectives™ on Stack Overflow

Adding comma separators to otherwise valid JSON string

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related