CSV to JSON Conversion in JavaScript

csv-to-json.js

//var csv is the CSV contents with headers
function csvJSON(csv){

  var lines=csv.split('\n');

  var result = [];

  var headers=lines[0].split(',');
  lines.splice(0, 1);
  lines.forEach(function(line) {
    var obj = {};
    var currentline = line.split(',');
    headers.forEach(function(header, i) {
      obj[header] = currentline[i];
    });
    result.push(obj);
  });

  return result; //JavaScript object
  //return JSON.stringify(result); //JSON
}

// ref: http://stackoverflow.com/a/1293163/2343
// This will parse a delimited string into an array of
// arrays. The default delimiter is the comma, but this
// can be overriden in the second argument.
function CSVToArray( strData, strDelimiter ){
    // Check to see if the delimiter is defined. If not,
    // then default to comma.
    strDelimiter = (strDelimiter || ",");

    // Create a regular expression to parse the CSV values.
    var objPattern = new RegExp(
        (
            // Delimiters.
            "(\\" + strDelimiter + "|\\r?\\n|\\r|^)" +

            // Quoted fields.
            "(?:\"([^\"]*(?:\"\"[^\"]*)*)\"|" +

            // Standard fields.
            "([^\"\\" + strDelimiter + "\\r\\n]*))"
        ),
        "gi"
        );


    // Create an array to hold our data. Give the array
    // a default empty first row.
    var arrData = [];
    var headers = [];
    var headersFound = false;
    var headerIndex = 0;

    // Create an array to hold our individual pattern
    // matching groups.
    var arrMatches = null;


    // Keep looping over the regular expression matches
    // until we can no longer find a match.
    while (arrMatches = objPattern.exec( strData )){

        // Get the delimiter that was found.
        var strMatchedDelimiter = arrMatches[ 1 ];

        // Check to see if the given delimiter has a length
        // (is not the start of string) and if it matches
        // field delimiter. If id does not, then we know
        // that this delimiter is a row delimiter.
        if (strMatchedDelimiter.length && strMatchedDelimiter !== strDelimiter){

            // Since we have reached a new row of data,
            // add an empty row to our data array.
            arrData.push( {} );
            headersFound = true;
            headerIndex = 0;
        }

        var strMatchedValue;

        // Now that we have our delimiter out of the way,
        // let's check to see which kind of value we
        // captured (quoted or unquoted).
        if (arrMatches[ 2 ]){

            // We found a quoted value. When we capture
            // this value, unescape any double quotes.
            strMatchedValue = arrMatches[ 2 ].replace(new RegExp( "\"\"", "g" ),"\"");

        } else {

            // We found a non-quoted value.
            strMatchedValue = arrMatches[ 3 ];

        }


        // Now that we have our value string, let's add
        // it to the data array.
        if (!headersFound) {
          headers.push(strMatchedValue);
        } else {
          arrData[arrData.length -1][headers[headerIndex]] = strMatchedValue;
          headerIndex ++;
        }
    }

    // Return the parsed data.
    return( arrData );
}

function csvFileToJSON(file) {
  if (!window.FileReader || !window.File) {
    return Promise.reject('Does not support File API');
  }
  if (!(file instanceof File)) {
    return Promise.reject('Not a file');
  }

  return new Promise(function(resolve, reject) {
    var reader = new FileReader();

    reader.onerror = function(err) {
      reject(err);
    };

    // Closure to capture the file information.
    reader.onload = function() {
      var text = reader.result;
      resolve(CSVToArray(text));
    };

    // Read in the image file as a data URL.
    reader.readAsText(file);
  });
}

CSVToArray from http://stackoverflow.com/a/1293163/2343 is better than the original because it handles strings in quotes
Updated to return array of objects instead of array of arrays.

what if the csv file is more than 1 GB