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]

score 68 · Accepted Answer · answered Aug 04 '12 at 01:20

68

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.

answered Aug 04 '12 at 01:20

Brad

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Thank you. but how to pars JSON in server side and use it? – Iman Marashi Apr 19 '18 at 20:11
Thank you again . I have read most of them. But they use the String variable. – Iman Marashi Apr 19 '18 at 21:51

score 11 · Answer 2 · answered May 18 '13 at 10:16

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.

score 9 · Answer 3 · edited Oct 16 '12 at 03:35

9

socket.send() doesn't understand object but it enjoys with JSON. You can use this way:

socket.send(JSON.stringify(myObject));

And use JSON.parse(json) to parse JSON to Object.

edited Oct 16 '12 at 03:35

Toribio

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answered Oct 16 '12 at 03:32

SaliproPham

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score 5 · Answer 4 · edited Dec 10 '14 at 00:18

5

Try using this on your server-side

socket.json.send({ your : 'data' });

and the JSON.parse() method on your client-side.

edited Dec 10 '14 at 00:18

Jack

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answered Apr 25 '14 at 17:17

Salman

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Works like a charm for me when sending to my Android-client, cheers! – Jack Dec 09 '14 at 23:47

score 3 · Answer 5 · answered Apr 06 '21 at 03:13

In socket.io V4.x, there is no need to use JSON.stringify():

There is no need to run JSON.stringify() on objects as it will be done for you.

e.g.

// BAD
socket.emit("hello", JSON.stringify({ name: "John" }));

// GOOD
socket.emit("hello", { name: "John" });

Socket.io how to send JavaScript object

5 Answers5

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