Is socket.io emit callback appropriate?

node.js callback socket.io emit
antanas_sepikas picture antanas_sepikas · Dec 2, 2013 · Viewed 42.8k times · Source

Recently I have been messing around with socket.io and found this interesting thing, that I can have emit function callback like this.

I start emitting on client side like this:

client.emit('eventToEmit', dataToEmit, function(error, message){
    console.log(error);
    console.log(message);
});

Then I can fire a callback from server-side like this:

client.on('eventToEmit', function(data, callback){
    console.log(data);
    callback('error', 'message');
});

Everything works fine with no errors, but I am interested if doing something like this is appropriate since I have not seen anything similar in the documentation or any example so far.

Answer

robertklep picture robertklep · Dec 2, 2013

It's perfectly legal.

Those callbacks are called 'acknowledgement functions' and are summarily mentioned in the Wiki and described a bit more in detail on the NPM page ('Getting acknowledgements').

EDIT: more recent documentation can be found here.

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