需要访问JSON.stringify对象中的数据

Question

The background for this question is I'm trying to access the selected cell from addListener in google visualization calendar. I could print the selected cell using JSON.stringify(chart.getSelection()); . It prints as [{"date":1468195200000,"row":0}] .

My problem is to access this date object. I tried to access it as

var obj=JSON.stringify(chart.getSelection());
        console.log('selected value '+obj.date);

But it displays as Undefined . When I print the obj it displays as [object, object]

If you need more information please let me know. Any suggestion would be appreciated.

Answer 1

JSON.stringify() serializes a data object into a string. Just access the object directly.

var data = chart.getSelection()[0]; // assuming there is only ever one item in the selection array.
console.log(data.date)

Answer 2

Try this:

 var data = [{"date":1468195200000,"row":0}] var rw = data[0].row; var dt = new Date(data[0].date); console.log(rw); console.log(dt); 

Answer 3

careful when accessing the first array element directly when listening for the 'select' event

chart.getSelection()[0]

the 'select' event is fired, both when a selection is made, AND removed

so the above line will fail when the selection is removed

check the length before accessing...

  selection = chart.getSelection();
  // check selection length
  if (selection.length > 0) {
    console.log(selection[0].date);
  } else {
    console.log('selection removed');
  }

see following working snippet, select a date, then select again to remove the selection...

 google.charts.load('current', { callback: function () { var dataTable = new google.visualization.DataTable(); dataTable.addColumn({ type: 'date', id: 'Date' }); dataTable.addColumn({ type: 'number', id :'Score' }); dataTable.addRows([ [ new Date(2016, 3, 13), 101 ], [ new Date(2016, 3, 14), 102 ], [ new Date(2016, 3, 15), 103 ], [ new Date(2016, 3, 16), 104 ], [ new Date(2016, 3, 17), 105 ] ]); var chart = new google.visualization.Calendar(document.getElementById('chart_div')); google.visualization.events.addListener(chart, 'select', function () { var selection = chart.getSelection(); // check selection length if (selection.length > 0) { console.log(selection[0].date); } else { console.log('selection removed'); } }); chart.draw(dataTable); }, packages:["calendar"] }); 

 <script src="https://www.gstatic.com/charts/loader.js"></script> <div id="chart_div"></div> 

Answer 4

This is an array of objects however there is only one object in this array (or so I think) so what you should do is console.log(obj[0].date); instead!