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Emit cheatsheet

io.on("connection", (socket) => {

// sending to the client
socket.emit("hello", "can you hear me?", 1, 2, "abc");

// sending to all clients except sender
socket.broadcast.emit("broadcast", "hello friends!");

// sending to all clients in "game" room except sender
socket.to("game").emit("nice game", "let's play a game");

// sending to all clients in "game1" and/or in "game2" room, except sender
socket.to("game1").to("game2").emit("nice game", "let's play a game (too)");

// sending to all clients in "game" room, including sender
io.in("game").emit("big-announcement", "the game will start soon");

// sending to all clients in namespace "myNamespace", including sender
io.of("myNamespace").emit("bigger-announcement", "the tournament will start soon");

// sending to a specific room in a specific namespace, including sender
io.of("myNamespace").to("room").emit("event", "message");

// sending to individual socketid (private message)
io.to(socketId).emit("hey", "I just met you");

// WARNING: `socket.to(socket.id).emit()` will NOT work, as it will send to everyone in the room
// named `socket.id` but the sender. Please use the classic `socket.emit()` instead.

// sending with acknowledgement
socket.emit("question", "do you think so?", (answer) => {});

// sending without compression
socket.compress(false).emit("uncompressed", "that's rough");

// sending a message that might be dropped if the client is not ready to receive messages
socket.volatile.emit("maybe", "do you really need it?");

// sending to all clients on this node (when using multiple nodes)
io.local.emit("hi", "my lovely babies");

// sending to all connected clients
io.emit("an event sent to all connected clients");

});

Note: The following events are reserved and should not be used as event names by your application:

  • connect
  • connect_error
  • disconnect
  • disconnecting
  • newListener
  • removeListener
// BAD, will throw an error
socket.emit("disconnecting");
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