Flattening of Array to comma separated values?

[cstrat]

If I have a JSON object with the following data:

{
  "Name": "test",
  "Tags": ["A", "B", "C"],
}

Converting this to CSV I'd like it to look like this:

Name,Tags
test, "A,B,C"

It's easy enough to manipulate the data prior to sending it to json-2-csv, but not sure if there are any plans for custom data hooks/manipulation.

[mrodrig]

Hi @cstrat. Thanks for asking. Currently the only data manipulation hook that's implemented for the json2csv method is the parseValue function type option. If you pass a function in using that key in the options object, you'll be able to manipulate the specific field value that's passed to the provided parseValue function. For example:

import converter from 'json-2-csv';

const csv = await converter.json2csvAsync([
    {
        "Name": "test",
        "Tags": ["A", "B", "C"],
      }
], {
  parseValue: (value) => {
      if (Array.isArray(value)) {
        return value.join(',');
      }
      return value;
  }
});

console.log(csv);

Which outputs:

Name,Tags
test,"A,B,C"

This overrides the default field value conversion method that's included in the module, and can be found here: https://github.com/mrodrig/json-2-csv/blob/stable/lib/json2csv.js#L316

Are there other data manipulation hooks that you think would be beneficial?

[cstrat]

Thanks for the response!
I wasn't looking close enough at the docs to notice that.

I'm using a different CSV to JSON converter (csvtojson) which has hooks based on CSV header so I was hoping this had something similar based on a JSON attribute, but this is all I really need.

[mebibou]

I have tried the snippet above and it gives me this error with the version 3.14.4:

TypeError: fieldValue.includes is not a function
    at wrapFieldValueIfNecessary (./node_modules/json-2-csv/lib/json2csv.js:358:24)

Also, the parseValue is no in the type definition

[mebibou]

Ok found the problem, when doing

parseValue: (value) => {
      if (Array.isArray(value)) {
        return value.join(',');
      }
      return value;
  }

If value is null, the function will simply crash. Need to make sure to return a string no matter what.

Type definitions would still be nice though