Document jQuery.Deferred.exceptionHook

[mgol]

See https://jquery.com/upgrade-guide/3.0/#callback-exit, in particular the paragraph:

Note that jQuery logs a message to the console when it is inside a Deferred and a JavaScript exception occurs. These messages take the form jQuery.Deferred exception: (error message). If you do not want any console output on these exceptions, set jQuery.Deferred.exceptionHook to undefined. If you need further help in finding errors reported this way, use the jquery-deferred-reporter plugin during development to obtain stack traces.

Here's the source code of this API: https://github.com/jquery/jquery/blob/cb8ab6ccdb8a7b843301793d4b7138a5a3750d6b/src/deferred/exceptionHook.js

[mgol]

PR: #1277