Why is my async/await implementation not wokring?-CodePudding

I have a list of csv-files and want to parse them. For this I imported fast-csv. I tried to implement the functionality as described in another stack overflow thread.

But in my code it does not work, and I am really confused why it does not work. I always get an empty array as output for log(data).

import { ParserOptionsArgs, parseFile } from '@fast-csv/parse'
import fs from 'fs'
import path from 'path'

var files: string[] = []
fs.readdirSync(inArg).forEach((file) => {
  files.push(path.parse(file).name)
})

files.forEach( async(file) => {
    const data: any = await readCsv(`${inArg}/${file}.csv`, { headers: true }, (row) => {})
    log(data)
    // here I want make some useful with the data
})

function readCsv(path: string, options: ParserOptionsArgs | undefined, rowProcessor: (arg0: any) => any) {
  return new Promise((resolve) => {
    const data: any = []

    parseFile(path, options)
      .on('data', (row: any) => {
        const obj = rowProcessor(row)
        if (obj) {
          data.push(obj)
          log(obj)
        }
      })
      .on('end', () => {
        resolve(data)
        log('Done')
      })
  })
}

The console output:

Files: [ 'test1', 'test2', 'test3', 'test4' ]
Done
[]
Done
[]
Done
[]
Done
[]

May someone can help me out?

CodePudding user response：

Your async/await code is fine. BUT: You are passing a rowProcessor function of

(row) => {}

to your readCsv. This rowProcessor doesn't return anything. I know it's a subtle pitfall, I stumbled upon this more than once. But how it's written above, the {} does not define an object, but an empty function body. If you really intend to return an empty object your rowProcessor should be

(row) => { return {}; }

(row) => ({})

Now, as your rowprocessor doesn't return anything, in the following snippet

const obj = rowProcessor(row)
if (obj) {
  data.push(obj)
  log(obj)
}

obj will of course always be undefined thus, nothing is pushed to your data array and hence log(data) will log the empty array, we see.