Javascript yyyy-mm-dd转换为不正确的日期(mm/dd/yyyy)

function convertDateFormat(dateString) {
  var dateParts = dateString.split("-");
  var year = parseInt(dateParts[0]);
  var month = parseInt(dateParts[1]);
  var day = parseInt(dateParts[2]);

  var date = new Date(year, month - 1, day);

  var convertedMonth = (date.getMonth() + 1).toString().padStart(2, "0");
  var convertedDay = date.getDate().toString().padStart(2, "0");
  var convertedYear = date.getFullYear().toString();

  var convertedDateString = convertedMonth + "/" + convertedDay + "/" + convertedYear;

  return convertedDateString;
}

var inputDateString = "yyyy-mm-dd";
var convertedDateString = convertDateFormat(inputDateString);
console.log(convertedDateString);