WebSocket: readyState property

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

The WebSocket.readyState read-only property returns the current state of the WebSocket connection.

A number which is one of the four possible state constants defined on the WebSocket interface:

WebSocket.CONNECTING (0): Socket has been created. The connection is not yet open.
WebSocket.OPEN (1): The connection is open and ready to communicate.
WebSocket.CLOSING (2): The connection is in the process of closing.
WebSocket.CLOSED (3): The connection is closed or couldn't be opened.

Specification
WebSockets Standard # ref-for-dom-websocket-readystate①

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