Socket.io how to send JavaScript object


Question

How to send JavaScript Object with Socket.io from server to client? I'm using Socket.io as WebSocket(sending with .send() and listen with message event). When I'm trying to do something like on server-side:

var myObject = {
    message: 'Hello World!'
}

socket.send(myObject);

on client-side I'm getting only this String: [object Object]

1
29
5/18/2013 10:18:15 AM

Accepted Answer

You actually need to emit an event instead:

 socket.emit('yourEvent', myObject);

If you use .send(), you are simply sending the string representation of your object, which is where the problem is occurring. Note that you can use .send(), but you would have to JSON-encode the object first, and decode it on reception.

Unless you have a specific reason, it's best to use the standard Socket.IO .emit() method, as it does all of this for you. That's what it is there for.

44
8/4/2012 1:20:14 AM

I just ran into this issue using some older example. Here is the answer I found: Migrating 0.6 to 0.7+, which I reproduce below.


In v0.6, socket.send would automatically convert an object like {a: 'b'} to JSON. You would send data to a client with:

socket.send({a: 'b'});

While this is cool, it poses a fundamental problem. JSON not only encodes objects, but also strings, numbers, etc! So, the API is more clear if you explicitly state you want to pass JSON (since there's a performance penalty associated with encoding/decoding JSON).

In v0.7, use the json flag:

socket.json.send({a: 'b'});

Now you can also emit and receive custom events between the browser and server:

socket.emit('my_event', {a: 'b'});

Arguments for events get encoded in JSON automatically for you.


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