Convert first property to keys

Question

I am using the following function to parse a csv file.

export default function readCsv (csv, reviver) {
  reviver = reviver || function(r, c, v) {
    return v;
  };
  let chars = csv.split(''),
    c = 0,
    cc = chars.length,
    start, end, table = [],
    row;
  while (c < cc) {
    table.push(row = []);
    while (c < cc && '\r' !== chars[c] && '\n' !== chars[c]) {
      start = end = c;
      if ('"' === chars[c]) {
        start = end = ++c;
        while (c < cc) {
          if ('"' === chars[c]) {
            if ('"' !== chars[c + 1]) {
              break;
            } else {
              chars[++c] = '';
            } // unescape ""
          }
          end = ++c;
        }
        if ('"' === chars[c]) {
          ++c;
        }
        while (c < cc && '\r' !== chars[c] && '\n' !== chars[c] && ',' !== chars[c]) {
          ++c;
        }
      } else {
        while (c < cc && '\r' !== chars[c] && '\n' !== chars[c] && ',' !== chars[c]) {
          end = ++c;
        }
      }
      row.push(reviver(table.length - 1, row.length, chars.slice(start, end).join('')));
      if (',' === chars[c]) {
        ++c;
      }
    }
    if ('\r' === chars[c]) {
      ++c;
    }
    if ('\n' === chars[c]) {
      ++c;
    }
  }
  return table;
}

The json looks like this:

What I want the json to look like is as follows:

[
    doc_id: "16278",
    framework_id: "8078",
    ...
],
[
    doc_id: "16261",
    framework_id: "880",
    ...
],

Basically, instead of getting the first row's content as the first value in the json, the first row should be converted into keys and rest of the rows into values.

Answer 1

It's relatively trivial to post-process your data to map it into the desired format, i.e. given the output from the CSV reader in variable data:

data = data.slice(1).map(function(row) {
    return row.reduce(function(obj, value, index) {
        var key = data[0][index];  // extract from first original row
        obj[key] = value;
        return obj;
    }, {});
});

i.e. iterate over all rows (skipping the 1st), creating an object based on the keys from the zeroth row and the values from the current.

Note that this will use the original keys in their long form. You may wish to change the values in the first row to make them more normalised first, e.g.:

data[0] = data[0].map(function(key) {
    key = key.replace(/[^\w\d\s]/g, ''); // strip non-alphanum or space
    return key.replace(/\s/g, '_').toLowerCase();
});

Answer 2

This is an efficient approach:

function csvToKeyedArray(csv) {
  var data = [];
  var keys = csv[0];
  var datum, entry, index;

  for (index in keys) {
    keys[index] = keys[index]
      .replace(/[^\w ]+/g, '') // remove extraneous characters like '?'
      .replace(/ /g, '_') // replace spaces with _
      .toLowerCase();
  }

  for (entry = 1; entry < csv.length; entry++) {
    // initialize an object for each row and add it to the `data` array
    data[entry - 1] = datum = {};

    for (index in keys) {
      // convert rows to objects
      datum[keys[index]] = csv[entry][index];
    }
  }

  return data;
}

data is then populated to your specifications.

This will be preferable to using .map() if your CSV file contains 10000's of rows, as the overhead of context-switching due to the function call for each iteration will cause it to be noticeably slower.

However, if your CSV file is expected to only be a few hundred or thousand rows, then using .map() will likely be preferable for readability and maintainability.

Answer 3

Try this one:

const csvData = `
    id,first_name,last_name,email,gender,ip_address
    1,Jami,Dumingos,jdumingos0@opensource.org,Female,209.112.103.56
    2,Brenda,Harbach,bharbach1@addtoany.com,Female,160.201.233.94
    3,Gail,Rowbrey,growbrey2@sakura.ne.jp,Female,160.199.58.40
    4,Ludvig,Coil,lcoil3@fotki.com,Male,158.37.136.163
    5,Lurlene,Conochie,lconochie4@skyrock.com,Female,145.147.12.44
    6,Aldous,Farrey,afarrey5@cargocollective.com,Male,44.148.54.88
    7,Skipp,Sket,ssket6@discovery.com,Male,81.190.215.227
    8,Greg,Wakefield,gwakefield7@yahoo.com,Male,105.157.167.96
    9,Westley,Purton,wpurton8@mapquest.com,Male,169.67.113.22
    10,Dill,Avraam,davraam9@google.de,Male,223.60.54.101`;

function readCsv(csv, splitMark = ',') {
  const lines = csv.split('\n');
  const keys = lines[0].split(splitMark); // first line as heading
  const rows = lines.slice(1, lines.length - 1);

  return rows.map(row => row
    .split(splitMark)
    .reduce((map, col, index) => {
      map[keys[index]] = col;
      return map;
    }, { }));
}

readCsv(csvData);