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rays0
16,293 PointsFirefox Issue
Firefox is not adding the 'responded' class when checkboxes are checked. Everytime the checkbox is checked I get the following in console: 'ReferenceError: event is not defined', 'app.js:21:9'
Tested on a webkit browser and worked fine.
1 Answer
Joel Kraft
Treehouse Guest TeacherPierrick is right, there is an error in the video. We'll fix this as soon as we can. Thanks for helping us catch this!
Explanation:
Chrome and Firefox handle the event variable differently. Chrome defines it, even if the developer hasn't! Firefox doesn't define event unless it is defined in the code. This is why you see the error in FF but not Chrome.
To avoid this issue, you always want to pass an argument into the handler, and use that argument to refer to the event object. So you could write:
DOMElement.addEventListener((e) => {
const element = e.target; // yay! :)
});
or
DOMElement.addEventListener((event) => {
const element = event.target; // yay! :)
});
but NOT
DOMElement.addEventListener((e) => {
const element = event.target; // boo! :(
});
and also NOT
DOMElement.addEventListener((event) => {
const element = e.target; // boo! :(
});
Does that make sense?
rays0
16,293 PointsThank you for the explanation Joel and Pierrick.
laurahenry
12,665 PointsGood explanation -- thanks, Joel!
Pierrick Le Roy
3,235 PointsPierrick Le Roy
3,235 PointsHello, this is because of a mistake in the video. Guil typed "event" instead of "e", that's why you got event is not defined. So just name correctly the Event Object to be "e".
Pierrick