JavaScript의 힙 정렬에 대한 자세한 설명

var len;    //因为声明的多个函数都需要数据长度，所以把len设置成为全局变量function buildMaxHeap(arr) {   //建立大顶堆  
    len = arr.length;  
    for (var i = Math.floor(len/2); i >= 0; i--) {  
        heapify(arr, i);  
    }}function heapify(arr, i) {     //堆调整  
    var left = 2 * i + 1,  
        right = 2 * i + 2,  
        largest = i;  
  
    if (left < len && arr[left] > arr[largest]) {  
        largest = left;  
    }  
  
    if (right < len && arr[right] > arr[largest]) {  
        largest = right;  
    }  
  
    if (largest != i) {  
        swap(arr, i, largest);  
        heapify(arr, largest);  
    }}function swap(arr, i, j) {  
    var temp = arr[i];  
    arr[i] = arr[j];  
    arr[j] = temp;}function heapSort(arr) {  
    buildMaxHeap(arr);  
  
    for (var i = arr.length-1; i > 0; i--) {  
        swap(arr, 0, i);  
        len--;  
        heapify(arr, 0);  
    }  
    return arr;}