如何改组数组?[重复]

2020/09/25 12:40 · javascript ·  · 0评论

我想改写JavaScript中的元素数组,如下所示:

[0, 3, 3] -> [3, 0, 3]
[9, 3, 6, 0, 6] -> [0, 3, 6, 9, 6]
[3, 3, 6, 0, 6] -> [0, 3, 6, 3, 6]

使用现代版本的Fisher-Yates随机播放算法

/**
 * Shuffles array in place.
 * @param {Array} a items An array containing the items.
 */
function shuffle(a) {
    var j, x, i;
    for (i = a.length - 1; i > 0; i--) {
        j = Math.floor(Math.random() * (i + 1));
        x = a[i];
        a[i] = a[j];
        a[j] = x;
    }
    return a;
}

ES2015(ES6)版本

/**
 * Shuffles array in place. ES6 version
 * @param {Array} a items An array containing the items.
 */
function shuffle(a) {
    for (let i = a.length - 1; i > 0; i--) {
        const j = Math.floor(Math.random() * (i + 1));
        [a[i], a[j]] = [a[j], a[i]];
    }
    return a;
}

但是请注意,截至2017年10月,将变量与解构分配交换会导致严重的性能损失。

var myArray = ['1','2','3','4','5','6','7','8','9'];
shuffle(myArray);

实施原型

使用Object.defineProperty从SO答案中获取的方法),我们还可以将该函数实现为数组的原型方法,而不必在诸如的循环中显示它for (i in arr)下面将允许您调用arr.shuffle()以随机排列数组arr

Object.defineProperty(Array.prototype, 'shuffle', {
    value: function() {
        for (let i = this.length - 1; i > 0; i--) {
            const j = Math.floor(Math.random() * (i + 1));
            [this[i], this[j]] = [this[j], this[i]];
        }
        return this;
    }
});

您可以使用Fisher-Yates Shuffle此网站改编的代码):

function shuffle(array) {
    let counter = array.length;

    // While there are elements in the array
    while (counter > 0) {
        // Pick a random index
        let index = Math.floor(Math.random() * counter);

        // Decrease counter by 1
        counter--;

        // And swap the last element with it
        let temp = array[counter];
        array[counter] = array[index];
        array[index] = temp;
    }

    return array;
}
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