TypeScript: Modern JavaScript Development

Implementing the AI using Minimax

We create an AI based on Minimax. The computer cannot know what his opponent will do in the next steps, but he can check what he can do in the worst-case. The minimum outcome of these worst cases is maximized by this algorithm. This behavior has given Minimax its name.

To learn how Minimax works, we will take a look at the value or score of a grid. If the game is finished, we can easily define its value: if you won, the value is 1; if you lost, -1 and if it is a draw, 0. Thus, for player 1 the next grid has value 1 and for player 2 the value is -1:

X|X|X
-+-+-
O|O| 
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X|O|

We will also define the value of a grid for a game that has not been finished. We take a look at the following grid:

X| |X
-+-+-
O|O|