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Start your free trialDustin Henry
7,392 PointsWhy do we do xhr.onreadystatechange = function instead of xhr.onreadystatechange(function)?
For instance, if I was adding an Event Handler to a DOM level object, I would do object.addEventListener('click', function), but with the onreadystatechange event handler, an equals sign is used instead. Why is that? Thank you for the help!
1 Answer
Steven Parker
231,110 PointsThe "addEventListener" method establishes an event handler for an object, but "onreadystatechange" is an event handler.
It might make more sense if we compare two ways of setting up "myClickHandler" on some object:
myButton.addEventListener('click', myClickHandler); // this is one way
myButton.onclick = myClickHandler; // this is another
Both of those do (almost) the same thing. The advantage of "addEventListener" is that you can attach more than one handler that way.