Help debug the code

Question

The active field continues below the grid.

Uncaught TypeError: Cannot read property '8' of undefined
Line: 253

https://code.sololearn.com/Wvo0ah19cC3q/?ref=app

Answer 1

Vasiliy

The entire canvas is active, if click anywhere on it the Game.prototype.tileAt() will be invoked. But clicking anywhere below the grid will cause an error because you are trying to access an element of a row that is not there or in other words, you are trying to access the property of an object that doesn't exist.

Using optional chaining operator(?.) should get rid of the Uncaught TypeError

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining

254 return this.grid[row]?.[col];

https://code.sololearn.com/W85HDPUJ4QvP/#js

Answer 2

ODLNT, Excellent! 👍👏
You are the best, I have been struggling with this for several days and no one responded.
I didn't even know about such a simple way to solve the problem.
But in principle, I also thought of inserting an exclusion condition here yesterday. ☺️
But I would like to make only the grid active.🤔

Answer 3

Vasiliy

Optional Chaining Operator is a part of the ES11/ ES2020 version.

https://medium.com/better-programming/8-new-features-shipping-with-es2020-7a2721f710fb
Link above is to an article about some other new features you may find interesting.

As for making only the grid active, I must admit I'm stumped maybe some of the more brilliant community members can help with that.

Either way, I'm glad I was able to help some.

Keep coding!