The WebSocket() constructor returns a new WebSocket object.


var ws = new WebSocket("ws://localhost:8080");


The URL to which to connect; this should be the URL to which the WebSocket server will respond.
protocols Optional
Either a single protocol string or an array of protocol strings. These strings are used to indicate sub-protocols, so that a single server can implement multiple WebSocket sub-protocols (for example, you might want one server to be able to handle different types of interactions depending on the specified protocol). If you don't specify a protocol string, an empty string is assumed.

Exceptions thrown

The port to which the connection is being attempted is being blocked.


Specification Status Comment
HTML Living Standard
The definition of 'WebSocket()' in that specification.
Living Standard Initial definition

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Contributors to this page: Claas
Last updated by: Claas,