Bug with "dataset" property in a memory card game

JavaScript
1

So I´m following a tutorial on Youtube which by the way is from FreeCodeCamp, and is about making a card memory game on JS. https://www.youtube.com/watch?v=ZniVgo8U7ek

Everything in my code semms to be working fine until I reach the minute 22:50 where it starts to put the conditional:

if(frontCard.dataset.framework === backCard.dataset.framework){
		frontCard.removeEventListener("click", changed);
		backCard.removeEventListener("click", changed);
	} else {
		frontCard.classList.remove('flip')
		backCard.classList.remove('flip')
	}

Once I update my code with that, I go click one of the cards and the error: “Cannot read property ‘dataset’ of undefined” appears. While in the video it doesn´t. Also, it doesn´t let me click more than one card before it resets again. While in the video it can click two cards. I seriously don´t understand what is happening.

This is the full code: https://codepen.io/Assblack/pen/jjrqrx Note that since I´m developing in my “local machine” the images won´t load, but you can see the error if you open the console, and hit any of the cards. An error with the text “Cannot read property ‘dataset’ of undefined” should appear.

3

Thanks, I just realized i put this.classList.toggle(‘flip’) instead of this.classList.add(‘flip’). I changed now and functionality seems to be working like it should although the error still appears.

What you talking about I get what you mean although that´s how she does it in the tutorial.