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JavaScript Callback Functions in JavaScript Callbacks and the DOM Using the Same Callback on Multiple Elements

karan Badhwar
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karan Badhwar
Web Development Techdegree Graduate 18,135 Points
Posted by karan Badhwar
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karan Badhwar
Web Development Techdegree Graduate 18,135 Points

event object as a parameter

How can we pass the event object, isn't that suppose to be in the scope of the event handler?

Secondly, we did not even mention that as an argument, so how the event caught is for the Input only? How the event Handler passed the event object.

Lastly, If I pass, It gives error, why so, the event is automatically being passed still? 

messageTextArea.addEventListener('focus', focusHandler(e))

1 Answer

Steven Parker
Steven Parker
231,275 Points
Steven Parker
Steven Parker
231,275 Points

The event object argument is passed by the system when it invokes your callback. You don't pass it yourself, you just receive the parameter when your function is called.

For more details, see the MDN page describing the event listener callback.