javascript数组“未定义”控制台日志

Question

I'd like to get 'roomname' out of the arrangement.. But when I run the log, I get undefined.

var roomNameArr = presenterArray.filter(function(item){
   console.log("## item.roomName : "+item.roomName);
   return item.roomName === viewerRoomName;
});

When I ran the log, the results below came out.

console.log("## roomNameArr : "+JSON.stringify(roomNameArr));

roomNameArr = [{"id":"1","pipeline":{"domain":null,"_events":{},"_eventsCount":7,"id":"5465b70f-613f-4184-80d3-895b3dcfa2c7_kurento.MediaPipeline"},"webRtcEndpoint":{"domain":null,"_events":{},"_eventsCount":6,"id":"5465b70f-613f-4184-80d3-895b3dcfa2c7_kurento.MediaPipeline/ac2bc699-bddf-44e2-a711-6444737109a1_kurento.WebRtcEndpoint"},"presenterRoomNum":"1","roomName":"1"}]

When I take a log to take out variable a, 'undefined' comes out.

console.log("## roomNameArr1 : "+roomNameArr['roomName']);
console.log("## roomNameArr1 : "+roomNameArr['5']);

I'm still wandering around and I need you to help me.

Answer 1

As roomNameArr is an array of objects, there is always an index number to all the objects within that array.

So if you want to access the key:value of any object within the roomNameArr array, you must have to define the index number on that object exists.

In your case, you have to write something like

console.log("## roomNameArr1 : "+roomNameArr[0]['roomName']);

or

console.log("## roomNameArr1 : "+roomNameArr[0].roomName);

to get the output correctly.