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JavaScript

Posted by Byron Farrell
Byron Farrell
5,700 Points

JavaScript event callback

Where is the "event" object coming from in this code 

DOM_Object.addEventListener('click', event => {
      //Do stuff
});

How is the event parameter getting the event object of the DOM_Object?

1 Answer

Michael Hulet
Michael Hulet
47,913 Points

JavaScript calls that function whenever DOM_Object is clicked. Sometimes, though, we'll want to know information about that event/click, so JavaScript also creates an object with potentially useful information about it and passes it to our handler function. That object is event in your code. Basically, JavaScript internally does this whenever a click happens on DOM_Object:

const clickDescription = { /* Tons of information about the click here */ };

yourClickHandlerFunction(clickDescription);

Later on in the code you posted, event is equal to clickDescription, which is an object describing the click event