I tried posting this before, but it seems to have gotten lost on the
internet.
One thing which is impossible to make in JavaScript today is a weakly
referenced event listener system. In such a system an event listener is not
strongly referenced by the event system, so events are only dispatched to
it as long as another object holds a reference to it. For example:
//some weak event system, could be global or created with constructor
var events = new WeakEventSystem();
(function(){
//This object only exists inside this IIFE, not outside it
var myObject = {
handler: function(event){
console.log("handle event: " + event);
}
};
//add a listener to events, but events only has a weak reference to it
events.addEventListener("someEvent", myObject.handler);
//the following causes the handler above to be called, resulting in
output on the console
events.dispatchEvent("someEvent", {params:"someParams"});
})();
//myObject does not exist anymore
//the following does not output anything on the console
events.dispatchEvent("someEvent", {params:"someParams"});
In this example the event system does not hold a strong reference to the
listener/handler function, so if nothing else has a reference to the
handler function, it is garbage collected.
Any thoughts on this, as an alternative to the more general (and low level)
weak references?
Marius Gundersen
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