Function can't make changes in the object??

Question

I wrote the following code in which ad() changes the value of tyer in the given obj. But the value is always returned nan and the object remains the same.
https://code.sololearn.com/Wxa8Nx4W0gu5/?ref=app

Answer 1

Use function instead of an arrow function. An arrow function is not bind to this (I can't explain clearly because I'm new to JS, sorry 🙄).

ad : function() {
// your code
}

Answer 2

That finally worked😲😄😄 thanks a lot. I'am really intrigued to know the reason behind this.