洗牌算法

function random(m, n) {
    return m + Math.floor(Math.random() * n);
}

function randomItem(arr, from = 0, to = arr.length) {
    const index = random(from, to);
    return {
        index,
        value: arr[index],
    };
}

function shuffle(arr) {
    for (let i = arr.length; i > 0; i--) {
        const { index } = randomItem(arr, 0, i);
        [arr[index], arr[i - 1]] = [arr[i - 1], arr[index]];
    }
    return arr;
}

　　经典洗牌算法,随机排列一次