script.html

<script type="text/javascript" src="../../utils/sort.js"></script>

<script code-main>
    const mergeSort = (array) => {
        let temp;
        let another = [];

        for (let i = 1, l = array.length; i < l; i *= 2) {
            // 跳格, 而且如果最后只剩一组了, 就不要再比了
            for (let j = 0; j < l - i; j += i * 2) {
                let cur = j;
                let first = j;
                let last = j + i;
                const end = Math.min(j + i * 2, l);

                while (first < j + i && last < end) {
                    if (array[first] <= array[last]) {
                        // 前面的小于等于后面的, 就先搞前面的, 保持整体有序
                        another[cur] = array[first];
                        ++first;
                    } else {
                        another[cur] = array[last];
                        ++last;
                    }

                    ++cur;
                }

                if (first < j + i) {
                    // 前面没处理完
                    for (; first < j + i; ++first, ++cur) {
                        another[cur] = array[first];
                    }
                } else if (last < end) {
                    for (; last < end; ++last, ++cur) {
                        another[cur] = array[last];
                    }
                }
            }

            // 如果就是最后只剩单独一组的情况, 要把这一组拷过去
            if (l % (i * 2) <= i) {
                for (let j = l - (l % (i * 2)); j < l; ++j) {
                    another[j] = array[j];
                }
            }

            temp = another;
            another = array;
            array = temp;
        }

        return array;
    };

    let origin = [9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 7, 7, 7];

    origin = mergeSort(origin);

    console.log('sort result:', origin);
</script>