CloseEvent.code

The code read-only property of the CloseEvent interface returns the close code sent by the server.

Value

A status code. As detailed in the following table, sourced from the IANA website:

Status code	Name	Description
`0`–`999`		Reserved and not used.
`1000`	Normal Closure	The connection successfully completed the purpose for which it was created.
`1001`	Going Away	The endpoint is going away, either because of a server failure or because the browser is navigating away from the page that opened the connection.
`1002`	Protocol Error	The endpoint is terminating the connection due to a protocol error.
`1003`	Unsupported Data	The connection is being terminated because the endpoint received data of a type it cannot accept. (For example, a text-only endpoint received binary data.)
`1004`		Reserved. A meaning might be defined in the future.
`1005`	No Status Received	Indicates that no status code was provided even though one was expected.
`1006`	Abnormal Closure	Indicates that a connection was closed abnormally (that is, with no close frame being sent) when a status code is expected.
`1007`	Invalid frame payload data	The endpoint is terminating the connection because a message was received that contained inconsistent data (e.g., non-UTF-8 data within a text message).
`1008`	Policy Violation	The endpoint is terminating the connection because it received a message that violates its policy. This is a generic status code, used when codes 1003 and 1009 are not suitable.
`1009`	Message too big	The endpoint is terminating the connection because a data frame was received that is too large.
`1010`	Missing Extension	The client is terminating the connection because it expected the server to negotiate one or more extension, but the server didn't.
`1011`	Internal Error	The server is terminating the connection because it encountered an unexpected condition that prevented it from fulfilling the request.
`1012`	Service Restart	The server is terminating the connection because it is restarting. [Ref]
`1013`	Try Again Later	The server is terminating the connection due to a temporary condition, e.g. it is overloaded and is casting off some of its clients. [Ref]
`1014`	Bad Gateway	The server was acting as a gateway or proxy and received an invalid response from the upstream server. This is similar to 502 HTTP Status Code.
`1015`	TLS Handshake	Reserved. Indicates that the connection was closed due to a failure to perform a TLS handshake (e.g., the server certificate can't be verified).
`1016`–`1999`		Reserved for future use by the WebSocket standard.
`2000`–`2999`		Reserved for use by WebSocket extensions.
`3000`–`3999`		Available for use by libraries and frameworks. May not be used by applications. Available for registration at the IANA via first-come, first-serve.
`4000`–`4999`		Available for use by applications.

Note: The 1xxx codes are only WebSocket-internal and not for the same meaning by the transported data (like when the application-layer protocol is invalid). The only permitted codes to be specified in Firefox are 1000 and 3000 to 4999 [Source, Bug].

Examples

The following example prints the value of code to the console.

WebSocket.onclose = function(event) {
  console.log(event.code);
};

Specifications

Specification
HTML Standard (HTML) # dom-closeevent-code-dev

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`code`	15	12	8	10	≤15	6	≤37	18	8	≤14	6	1.0

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https://developer.mozilla.org/en-US/docs/Web/API/CloseEvent/code