Вынести переменные в метод

Подскажите как в даном примере

  if (mode === 'day') {
    return {
      title: date.format('dddd')
    }
  } else if (mode === 'week') {
    var momentArgument = (mode === 'week' ? 'isoWeek' : mode)
    var lineDate = getLineDate(date, momentArgument);
    var lineHeight = 90;
    var clientValue = lineHeight * clients.length;
    return {
      title: date.startOf(momentArgument).format('MMM') + ' ' + date.startOf(momentArgument).format('DD') + '-' + date.endOf(momentArgument).format('DD'),
      subtitle: 'Week ' + date.week(),
      isLine: lineDate.isLine,
      lineLeft: lineDate.lineLeft,
      lineHeight: clientValue + 'px'
    }
  } else if (mode === 'month') {
    var lineDate = getLineDate(date, mode);
    var lineHeight = 90;
    var clientValue = lineHeight * clients.length;
    return {
      title: date.format('MMMM'),
      daysInMonth: moment(date.format('YYYY-MM')).daysInMonth(),
      isLine: lineDate.isLine,
      lineLeft: lineDate.lineLeft,
      lineHeight: clientValue + 'px'
    }
  }

вынести строчки

var lineDate = getLineDate(date, mode);
var lineHeight = 90;
var clientValue = lineHeight * clients.length;

в отдельный метод