javascript - 加载图表后如何获取 Google Visualization DataTable 数据？

Question

我想从页面抓取 Google Chart 数据，将其转换为 CSV，然后将其交给下载程序。

在 chartpage.js 中

function downloadCSV(args) {
  var csvData, filename, link;
  var action = args.action_name;
  var csv = convertArrayOfObjectsToCSV({
    action_name: action
  });
  filename = args.filename || 'export.csv';

  csvData = encodeURI(csv);

  link = document.createElement('a');
  link.setAttribute('href', 'data:text/csv;charset=utf-8,' + csvData);
  link.setAttribute('type', 'data:text/csv;charset=utf-8');
  link.setAttribute('download', filename);
  link.click();
 }

然后在 chart.coffee 中:

 init_chart = ->
   chart = new google.visualization.BarChart(document.getElementById('chart_div'));  //#chart_div in chart.html.haml

render_chart = (items, year)->
  @data = new google.visualization.DataTable()
  data.addColumn 'string', I18n.t('charts.name')

  // Other logic for building chart from Rails DB Data

  for key_item in items
  label = []
  [key, item] = key_item.split(':')

  if key == 'competitor_meded_involvement'
    label.push I18n.t('charts.competitor')

  label.push I18n.t("kol_items.#{item}")

  data.addColumn 'number', label.join(' - ')

// and so on.

google.charts.load 'current', 'packages': ['corechart']

google.visualization.events.addListener(@data, 'ready', setData) // I read this was a solution but it doesn't seem to help

google.charts.setOnLoadCallback ->

init_chart()

render_chart()

$(setData(@data)) //I tried passing this to a setter method over in chartpage.js which takes @data and tries to set it globally but that makes no difference at page load time.

在 chart.html.haml 中:

 %h5{id: "downloadCSV"}= link_to '<i class="fa fa-file-excel-o"></i> Download CSV'.html_safe, "#"

 #chart_div

所以我在主 JS 中同时尝试以上和以下内容:

case 'chart_kol_comparison':
        google.setOnLoadCallback(function() {
          str = google.visualization.dataTableToCsv(window.data); //This builds the CSV string and returns it to the download JS for output
        });

但是来自页面 JS (HAML) 的数据变量:

 @data = new google.visualization.DataTable()

似乎只有在页面加载后才可用——当上面的 JS 加载并试图获取数据时不可用。

当我在控制台中运行以下命令时有效，但在页面加载时无效。这是在 Rails 应用程序中。

 str = google.visualization.dataTableToCsv(data); //var data is populated after page loads (available from console) but not from the JS at page load time.

我该怎么做？

Answer 1

这里似乎发生的事情是您没有在调用 draw 后等待图表/数据表完全呈现。因此，实现此目的的最佳方法是创建一个事件处理程序，等待图表/数据表的就绪事件。

google.visualization.events.addListener(tableChart, 'ready', myReadyHandler);

然后添加填充变量的函数，但要在图表/数据表准备好之后。

function myReadyHandler(){
  // fill variables here or call directly your other methods, 
  // this will ensure, you can grab data from the chart/datatable
  // because is completely rendered and you can play with that
}