Bubble sort and selection sort

冒泡排序 
for (let j = 0; j < a.length - 1; j++) {
            for (let i = 0; i < a.length - 1 - j; i++) {
                if (a[i] > a[i + 1]) {
                    temp = a[i + 1];
                    a[i + 1] = a[i];
                    a[i] = temp;
                }
            }
}
选择排序

for (let j = 0; j <length- 1;j++) {
            for (let i = j; i < length- 1; i++) {
                if (a[j] > a[i + 1]) {
                    temp = a[j];
                    a[j] = a[i + 1];
                    a[i + 1] = temp;
                }
            }
}