const handleFiles = event => {
  const f = event.target.files[0];
  const parser = CsvParse({delimiter: ',', columns: true});
  parser.on('readable', function(){
    console.log('readable');
    let record;
    // eslint-disable-next-line no-cond-assign
    while (record = parser.read()) {
      console.log(record);
    }
  });
  const reader = new FileReader();
  reader.onload = (function() {
    return function(e) {
      console.log('Writing');
      parser.write(e.target.result);
    };
  })(f);

  reader.readAsText(f);
};

Letter,Number
A,1
B,2
C,3

Writing
readable
{Letter: "A", Number: "1"}
readable
{Letter: "B", Number: "2"}