What is an event?

[sn...@olymega.org]

I am looking for what an event is in terms of its implementation.I know what an event is in the abstract sense:

https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Building_blocks/Events

For instance, everyone knows what a 'list' is - a term that applies equally to 'shopping list' as well as 'collection of data'. However, I'm more interested in event implementation, e.g. how a programming language implements lists as arrays and Objects. I would like to know how events exist concurrently as code in the browser (written in in C++) and as data. (picked by an event handler). 

Thank you! The official docs are sparse on how events are implemented. So far, I know that they are 'objects' though it's not clear whether these are objects v.v. C++ or JavaScript. 

[J Decker]

any of the above.

Events are a map of some sort of identifier and a callback.

For my websocket interface, which is C/C++ the events are tracked in C/C++ structures. 

For a graph database I was tinkering with in ES6, the events are tracked in just javascript ojects.

A super simple way (and I'm sure there's lots of ways of doing this)

var myObjectWithEvents = { events : {},

   on( event, callbackOrData ) {

       if( typeof callbackOrData === "function" ) {

            this.events[event] = callbackOrData;   // register event handler

       } else {

            if( event in this.events ) {

                this.events[event]( callbackOrData );  // invoke event handler

            }

       }

    }

};

myObjectWithEvents.on( "click", (data)=>{ console.log( "got click event..." ) } );   /// register an event handler to 'click'

....

myObjectWithEvents.on( "click", { x:1, y : 250 } );   // trigger an event...

Instead of assigning directly, each event in 'events' could be an array ... []  and .push( callbackOrData ); would allow you to assign multiple handlers to each eent instead of a single... and then you'd just  do something like    this.events[event].forEach( cb=> cb( callbackOrData ) ) instead.

The above was something I got from Gun DB; if the argument passed to 'on' is a function, keep that function as a callback stored as the name of the event specified.  If it's not a function, call any previously registered event with the data passed to 'on', which then overloads 'on' as both the uhh addEventListener()  and the emit().

[sn...@olymega.org]

Thank you for your reply. I guess I am wondering where and how JavaScript and C++ code/data interact. 

I assume that C++ and JavaScript compile/interpret into 'mutually intelligible' byte code. 

I also assume that Events are Data that are dispatched by the Browser upon, say, I/O. 

Then, JavaScript code, like yours above, can handle an Event once it has fired, caught and placed on queue by the Event Loop, which pushes it onto the Stack.