SOURCE

const cards = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H'];

Array.prototype.shuffle = function() {
    for (let i = cards.length - 1; i > 0; i--) {
        const randomIndex = Math.floor(Math.random() * (i - 1));
        const itemAtIndex = this[randomIndex];

        this[randomIndex] = this[i];
        this[i] = itemAtIndex;
    };
};

cards.shuffle();
console.log(cards);