Terminology – Difference Between Trigger, Handler, and Callback

conceptsterminology

It's current to see the terms callback, trigger and handler in some API documentations. It is just synonymous or each term correspond to a specific concept?

I used to think that this terms are just synonymous, but I must be wrong …

Thanks !

Best Answer

These are general terms in programming. Often can mean different things but generally speaking...

callback is a reference to a function or block of code that is executed by a third party.

trigger is a behavior in response to stimuli, and an event may trigger the change of state or as the result of that trigger execute the associated callback.

handler is a reference to an object or class that is associated with a behavior. A handler is different from a callback because it's an object that represents a state.

Using jQuery AJAX as an example.

$.ajax({
   url: "test.html",
   context: document.body
}).done(function() {
   $(this).addClass("done");
});
  • The function() is a callback.
  • The object passed to $.ajax(...) is a handler.
  • The event done() is a trigger.

The handler has an event done that when triggered calls the callback to perform $(this).addClass("done");.

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