The value function in the fields does not support the async function

[Kehao33]

import { parse } from "json2csv";

   const options = { 
          fields: [
            {
                label: "classLen", 
                value: async (row, _) =>
                  (
                    await this.someModel.find({classId: row?._id})
                  )?.filter((c) => c.students > 0)?.length,
                default: "0", 
              }
          ]
   }

const data = {classId: 12345};
console.log(parse(data, options));  

want: "classLen" "23"

but return: "classLen" "{}"

Filing an issue

"json2csv": "^5.0.6"

Thank you. The value function in the fields does not support the async function

[juanjoDiaz]

It does not.

This library convert JSON to CSV and allow some formatting features but not advanced data manipulation. Think of a dataset with millions of rows and hundreds of columns... The performance impact of allowing async function would be too high to make sense.

You can do the mapping by preprocessing data. But I still think that you should be re-thinking what you are doing... If you are doing API calls or db lookups you might be doing the same call a million times and DOSing your own services if the dataset gets big...

[knownasilya]

An alternative approach would be to find all of the db entities, and then look them up from that list instead.