socket.io/CHANGELOG.md

3.0.0-rc1 (2020-10-13)

Features

• add ES6 module export (8b6b100)
• do not reuse the Engine.IO id (2875d2c)
• remove Server#set() method (029f478)
• remove Socket#rooms object (1507b41)
• remove the 'origins' option (a8c0600)
• remove the implicit connection to the default namespace (3289f7e)
• throw upon reserved event names (4bd5b23)

BREAKING CHANGES

• the 'origins' option is removed

Before:

new Server(3000, {
  origins: ["https://example.com"]
});

The 'origins' option was used in the allowRequest method, in order to determine whether the request should pass or not. And the Engine.IO server would implicitly add the necessary Access-Control-Allow-xxx headers.

After:

new Server(3000, {
  cors: {
    origin: "https://example.com",
    methods: ["GET", "POST"],
    allowedHeaders: ["content-type"]
  }
});

The already existing 'allowRequest' option can be used for validation:

new Server(3000, {
  allowRequest: (req, callback) => {
    callback(null, req.headers.referer.startsWith("https://example.com"));
  }
});

• Socket#rooms is now a Set instead of an object

• Namespace#connected is now a Map instead of an object

• there is no more implicit connection to the default namespace:

// client-side
const socket = io("/admin");

// server-side
io.on("connect", socket => {
  // not triggered anymore
})

io.use((socket, next) => {
  // not triggered anymore
});

io.of("/admin").use((socket, next) => {
  // triggered
});

• the Server#set() method was removed

This method was kept for backward-compatibility with pre-1.0 versions.