convert CSV lines into Javascript objects

Using ES6/ES7 and some functional programming guidelines:

• All variables are const (immutability)
• Use map/reduce instead of while/for
• All functions are Arrow
• No dependencies

// Split data into lines and separate headers from actual data
// using Array spread operator
const [headerLine, ...lines] = data.split('\n');

// Split headers line into an array
// `valueSeparator` may come from some kind of argument
// You may want to transform header strings into something more
// usable, like `camelCase` or `lowercase-space-to-dash`
const valueSeparator = '\t';
const headers = headerLine.split(valueSeparator);

// Create objects from parsing lines
// There will be as much objects as lines
const objects = lines
  .map( (line, index) =>
    line
      // Split line with value separators
      .split(valueSeparator)

      // Reduce values array into an object like: { [header]: value }
      // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reduce
      .reduce(

        // Reducer callback 
        (object, value, index) => ({
          ...object,
          [ headers[index] ]: value,
        }),

        // Initial value (empty JS object)
        {}
      )
  );

console.log("Objects:", objects);

For CSV files using , as separator and quotes string values, you can use this version:

// Split data into lines and separate headers from actual data
// using Array spread operator
const [headerLine, ...lines] = data.split('\n');

// Use common line separator, which parses each line as the contents of a JSON array
const parseLine = (line) => JSON.parse(`[${line}]`);

// Split headers line into an array
const headers = parseLine(headerLine);

// Create objects from parsing lines
// There will be as much objects as lines
const objects = lines
  .map( (line, index) =>

    // Split line with JSON
    parseLine(line)

      // Reduce values array into an object like: { [header]: value } 
      .reduce( 
        (object, value, index) => ({
          ...object,
          [ headers[index] ]: value,
        }),
        {}
      ) 
  );

return objects;

Note: For big files, it would be better to work with streams, generators, iterators, etc.

By doing this:

arr = bufferString.split('\n'); 

you will have an array containing all rows as string

["fname, lname, uid, phone, address","John, Doe, 1, 444-555-6666, 34 dead rd",...]

You have to break it again by comma using .split(','), then separate the headers and push it into an Javascript Object:

var jsonObj = [];
var headers = arr[0].split(',');
for(var i = 1; i < arr.length; i++) {
  var data = arr[i].split(',');
  var obj = {};
  for(var j = 0; j < data.length; j++) {
     obj[headers[j].trim()] = data[j].trim();
  }
  jsonObj.push(obj);
}
JSON.stringify(jsonObj);

Then you will have an object like this:

[{"fname":"John",
  "lname":"Doe",
  "uid":"1",
  "phone":"444-555-6666",
  "address":"34 dead rd"
 }, ... }]

See this FIDDLE