The code checks if the device is in landscape mode....

The code checks if the device is in landscape mode. It first checks if the window.screen object exists, and if it does, it extracts the orientation property from it using destructuring assignment.

If the orientation property exists, the code checks if its type property starts with the string "landscape" by calling the indexOf() method on it and comparing the result to 0. If it does, the function returns true.

If the orientation property does not exist or its type does not start with "landscape", the code falls back to checking the window.orientation property. If its value is either 90 or -90, the function also returns true.

If none of these conditions are met, the function returns false.