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JavaScript JavaScript and the DOM (Retiring) Responding to User Interaction Functions as Parameters

Jan Livny
Jan Livny
6,705 Points

Functions in event listeners


Is it an obligation to use a function inside an event listener:

MyButton.addEventListener("click", () => {myHeading.style.color = "red"})

Or is it a style/ good practice thing, if so can I simply use:

MyButton.addEventListener("click", myHeading.style.color = "red")

Thanks in advance,


1 Answer

Brendan Whiting
.a{fill-rule:evenodd;}techdegree seal-36
Brendan Whiting
Front End Web Development Techdegree Graduate 84,697 Points

Yes, you pretty much have to use a function, cannot use a statement. In the example you provided, the statement will immediately run setting myHeading.style.color to "red". It won't wait for a click event to happen, it will happen as soon as the script loads. You also can see this error in the console:

The callback provided as parameter 2 is not an object.

Technically speaking, you could also use object implementing the EventListener interface according to the documentation. And, functions are objects too, so that error message could be a little bit confusing.

But the simple answer is: yes, it should be a function.