Google折线图h轴标签在图表绘制过程中消失

google.charts.load('current', {'packages':['corechart']});
google.charts.setOnLoadCallback(drawChart);

function drawChart() {
  var data = google.visualization.arrayToDataTable([
    ['Year', 'Sales', 'Expenses', 'Profit'],
    ['2013', 1000, 1000, 1000],
    ['2014', 1000, 1000, 1000],
    ['2015', 1000, 1000, 1000],
    ['2016', 1000, 1000, 1000]
  ]);

  var options = {
    title: 'Sales, Expenses and Profit over Years',
    hAxis: {
      title: 'Year',
      tickStep: 1
    }
  };

  var chart = new google.visualization.LineChart(document.getElementById('chart_div'));
  chart.draw(data, options);
}

google.charts.load('current', {'packages':['corechart']});
google.charts.setOnLoadCallback(drawChart);

function drawChart() {
  var data = google.visualization.arrayToDataTable([
    ['Year', 'Sales', 'Expenses', 'Profit'],
    ['2013', 1000, 1000, 1000],
    ['2014', 1000, 1000, 1000],
    ['2015', 1000, 1000, 1000],
    ['2016', 1000, 1000, 1000]
  ]);

  var options = {
    title: 'Sales, Expenses and Profit over Years',
    hAxis: {
      title: 'Year',
      tickStep: 1
    }
  };

  var chart = new google.visualization.LineChart(document.getElementById('chart_div'));
  chart.draw(data, options);
}