flatten_object.js

function trimNewlinesAndSpaces(inputString) {
  // Remove newlines and replace multiple spaces with a single space
  if (typeof inputString === "string") {
    return inputString.replace(/\n/g, '').replace(/ +/g, ' ').replace(/\,/g, '');
  } else {
    return "" + inputString
  }
}

const flattenObj = (results, parentKey, obj) => {
  for (let key in obj) {
    // console.log("key> ", key, obj[key], typeof obj[key])
    let newKey = parentKey ? `${parentKey}.${key}` : key;
    if (typeof obj[key] === "string" || typeof obj[key] === "number") {
      results[newKey] = results[newKey] || [];
      results[newKey].push(trimNewlinesAndSpaces(obj[key]))
    } else {
      if (Array.isArray(obj[key])) {
        let numbersOrStrings = obj[key].filter(item => typeof item === "string" || typeof item === "number")
        results[newKey] = results[newKey] || [];
        results[newKey] = results[newKey].concat(numbersOrStrings.map(trimNewlinesAndSpaces))

        let otherObjects = obj[key].filter(item => typeof item !== "string" && typeof item !== "number")
        otherObjects.map(flattenObj.bind(null, results, newKey))
      }
    }
  }
  return results;
};

const objectToCsv = (data) => {
  let longestArray = -1
  for (let key in data) {
    if (data[key].length > longestArray) {
      longestArray = data[key].length + 1
    }
  }

  let columns = []
  for (let key in data) {
    if (data[key].length > 0) {
      let row = new Array(longestArray).fill('')
      row[0] = key
      for (let i = 0; i < data[key].length; i++) {
        row[i + 1] = data[key][i]
      }
      columns.push(row)
    }
  }

  let lines = []
  for (let a = 0; a < longestArray; a++) {
    let line = []
    for (let j = 0; j < columns.length; j++) {
      line.push(columns[j][a])
    }
    lines.push(line)
  }

  console.log(lines.join("\n"))
}


if (require.main === module) {

  // Usage example
  let inputData = {
    name: "John",
    age: 30,
    hobbies: ["reading", "games", "coding"],
    experience: [{
      companyName: "Google",
      position: "Software Engineer",
      years: 2
    },
    {
      companyName: "Amazon",
      position: "QA Engineer",
      years: 3
    }]
  };

  let output = [
    "name, John",
    "age, 30",
    "hobbies, reading, games, coding",
    "experience.companyName, Google, Amazon",
    "experience.position, Software Engineer, QA Engineer",
    "experience.years, 2, 3",
  ]
  const outputData = flattenObj({}, "", inputData);

  console.log("outputData", outputData)

  objectToCsv(outputData)
}