Using variable keys to access values in JavaScript objects

Question

The code:

function updateDashboardData() {     $.getJSON("includes/system/ajaxDataInterface.php", {recordcount:1}, function(data) {         $('.stationContainer').each(function(data) {             var bsID = $(this).attr("id");             var bsStatus = $(this).children('.stationStatus');             alert(data[bsID][0].time);             bsStatus.find('.bs_maxHandsets').text(data[bsID][0].maxHandsets);             bsStatus.find('.bs_time').text(data[bsID][0].time);         });     }); } 

The object data:

{     "A5A50000": [{         "bsid": "A5A50000",         "chanCount": 17,         "time": "2009-05-27 16:36:45",         "avgInterference": 1.711765,         "maxInterference": 4.97,         "avgHandsets": 205.1176,         "maxHandsets": 315,         "avgCalls": 6.4118,         "maxCalls": 13,         "avgCBA": 3868.98059,         "maxCBA": 7463,         "sumSuccessCBA": 197318,         "sumTimeoutHandoff": 133,         "sumAttemptHandoff": 1028,         "sumDeniedHandoff": 216,         "sumConfirmHandoff": 679,         "sumHandoffNetwork": 61873,         "sumJoinNetwork": 96888,         "sumLeaveNetwork": 93754,         "sumRcvdKeepalive": 98773,         "sumTimeoutKeepalive": 19748,         "sumAttemptUplink": 93689,         "sumBlockedUplink": 62453     }] } 

The problem:

alert(data.A5A50000[0].time); properly displays "2009-05-27 16:36:45".

alert(bsID); properly displays "A5A50000".

alert(data.bsID[0].time); reports "data.bsID is undefined".

alert(data[bsID][0].time); reports "data[bsID] is undefined".

I'm a little unclear when a variable is/isn't evaluated. Maybe I'm overlooking something silly, but I can't figure out my problem here.

Answer 1

You can access object properties by dot notation or by bracket notation.

var x = {'test': 'hi'}; alert(x.test); // alerts hi alert(x['test']); // alerts hi 

When you have a dynamic value, you have to use the latter:

var property = 'test'; alert(x.property); // looks for x.property, undefined if it doesn't exist alert(x[property]); // looks for x['test'], alerts hi 

So what you actually want is:

alert(data[bsID][0].time); 

EDIT:

Not sure what you're doing wrong, but this is working for me on Firebug's console:

var data = {"A5A50000":[{"bsid":"A5A50000","chanCount":17,"time":"2009-05-27 16:36:45","avgInterference":1.711765,"maxInterference":4.97,"avgHandsets":205.1176,"maxHandsets":315,"avgCalls":6.4118,"maxCalls":13,"avgCBA":3868.98059,"maxCBA":7463,"sumSuccessCBA":197318,"sumTimeoutHandoff":133,"sumAttemptHandoff":1028,"sumDeniedHandoff":216,"sumConfirmHandoff":679,"sumHandoffNetwork":61873,"sumJoinNetwork":96888,"sumLeaveNetwork":93754,"sumRcvdKeepalive":98773,"sumTimeoutKeepalive":19748,"sumAttemptUplink":93689,"sumBlockedUplink":62453}]}; var bsID = 'A5A50000'; alert(data[bsID][0].time);