regularVsFunctional.js

function calculateWinner(squares) {
    const lines = [
        [0, 1, 2],
        [3, 4, 5],
        [6, 7, 8],
        [0, 3, 6],
        [1, 4, 7],
        [2, 5, 8],
        [0, 4, 8],
        [2, 4, 6],
    ];
    for (let i = 0; i < lines.length; i++) {
        const [a, b, c] = lines[i];
        if (squares[a] && squares[a] === squares[b] && squares[a] === squares[c]) {
            return squares[a];
        }
    }
    return null;
}

const calculateWinner = (squares) => {
    const lines = [
        [0, 1, 2],
        [3, 4, 5],
        [6, 7, 8],
        [0, 3, 6],
        [1, 4, 7],
        [2, 5, 8],
        [0, 4, 8],
        [2, 4, 6],
    ];

    const allXsOrOs = _.anyPass([
        _.all(_.equals('X')),
        _.all(_.equals('O'))
    ]);

    const pickLine = _.props(_.__, squares);

    return _.pipe(
        _.find(_.pipe(pickLine, allXsOrOs)),
        _.cond([
            [_.isNil, _.identity],
            [_.T, _.pipe(_.head, _.nth(_.__, squares))]
        ])
    )(lines);
};