socket.io-client - transports options array modified from [string] to [object] by io constructor

[esellier]

Describe the bug

const options = {transports: ["websocket","polling"]};
const s = io(<URL>, options);

options object is modified, and transports is set to [ class WS, class XHR ]
Not really a big issue, but quite unexpected and an unusual behaviour. Especially when you need to serialize the options object after connection.

Expected behavior
options object should not be mutated.

[esellier]

socket.io/packages/socket.io-client/lib/index.ts

Line 39 in 74599a6

opts = opts || {};

should be
opts = Object.assign({}, opts)