How to change classes on click and return everything back when you repeat?

Question

JavaScript

Need a pure JS solution.
I did the following https://jsfiddle.net/am0qj4y9/
I don't understand why it doesn't work.

TypeError: Cannot read property 'addEventListener' of undefined

Answer 1

Try it yourself https://www.w3schools.com/howto/howto_js_toggle_cl...