JavaScript 的广播频道是否仅限于每秒接收一条消息？

Question

I may have answered this question for myself but I need to sanity check...

I have one tab broadcasting to another over the broadcast channel every 500 ms. The second tab is set to receive broadcasts and print them in the console log.

Sending tab:

const crossTraffic = new BroadcastChannel('crossTraffic');

const queueInterval = setInterval(function(){
   crossTraffic.postMessage({action: 'keepalive', cTime: Date.now()});
   console.log(`cTime sent ${Date.now()}`);
    }
},500);

Receiving tab:

const crossTraffic = new BroadcastChannel('crossTraffic');

crossTraffic.onmessage = function(e){
  if (e.data.action === 'keepalive'){
      console.log(`ctime received ${e.data.cTime}`);
    }
  }

I've observed the following: no matter what I set the queueInterval time for, the receiving tab will never receive a broadcast more than once every 1,000 ms.

Is this normal behavior for the broadcast channel or is it possible to receive messages at a smaller interval than 1,000 ms?

Answer 1

This is a different issue than I thought...

Turns out that tabs that aren't the focus (at least in Chrome) are limited to one update per second. If I open separate windows and have one broadcast to the other, each message arrives at whatever interval I select (tested at 100ms).

Here's the modified code I used for testing on the sending window/tab:

const crossTraffic = new BroadcastChannel('crossTraffic');

var queueInterval;
var count = 0;

  queueInterval = setInterval(function(){
       count++
        if (count >= 100){
            clearInterval(queueInterval);
          }
       crossTraffic.postMessage({action: 'keepalive', cTime: Date.now(), count: count});
       console.log(`cTime sent ${Date.now()}`);
        }
    },100);

And the modified receiver:

const crossTraffic = new BroadcastChannel('crossTraffic');

crossTraffic.onmessage = function(e){
  if (e.data.action === 'keepalive'){
      console.log(`ctime received ${e.data.cTime}, #${e.data.count}`);
    }
  }

You'll observe that if both sender and receiver are tabs in the same window, the receiver will be logging them only once per second, yet all 100 messages will be sent and received.

Then, pull one of the tabs out into its own window and place them side by side, watching their logs: the message will send and receive at a 100 ms interval.

Overall, excellent news as I was afraid the broadcast channel had some strict limitations I was unaware of.

Now to determine how to force background tabs to update more than once per second...