如下图所示：使用数组来表示二叉树，可得
    堆 - 图1

    1. const parent = i => (i-1) >>> 1;
    2. const left = i => 1 + (i << 1);
    3. const right = i => 2 + (i << 1);
    1. const parent = i => (i-1) >>> 1;
    2. const left = i => 1 + (i << 1);
    3. const right = i => 2 + (i << 1);
    4. const swap = (nums, l, r) => [nums[l], nums[r]]=[nums[r], nums[l]];
    6. function toBottom(d, i, len, comp) {
    7.   while (i < len) {
    8.       let l = left(i), r = right(i), m = i;
    9.     if (l < len && comp(d[l], d[m]) <= 0) {
    10.       m = l;
    11.     }
    12.     if (r < len && comp(d[r], d[m]) <= 0) {
    13.       m = r;
    14.     }
    15.     if (m===i) break;
    16.     swap(d, i, m);
    17.     i = m;
    18.   }
    19. }
    21. function toUpper(d, i, comp) {
    22.   while (i) {
    23.     let p = parent(i);
    24.     if (comp(d[p], d[i]) <= 0) break;
    25.     swap(d, p, i);
    26.     i = p;
    27.   }
    28. }
    30. export class Heap {
    31.   constructor(comp = (a, b) => a - b) {
    32.     this.data = [];
    33.     this.comp = comp;
    34.   }
    35.   push(d) {
    36.     this.data.push(d);
    37.     toUpper(this.data, this.data.length - 1, this.comp);
    38.   }
    39.   peek() {
    40.     return this.data[0];
    41.   }
    42.   isEmpty() {
    43.     return this.data.length === 0;
    44.   }
    45.   pop() {
    46.     if (this.data.length <= 1) {
    47.       return this.data.pop();
    48.     }
    49.     const r = this.data[0];
    50.     this.data[0] = this.data.pop();
    51.     toBottom(this.data, 0, this.data.length - 1, this.comp);
    52.     return r;
    53.   }
    54.   static sort(arr, comp) {
    55.     for (let i = (arr.length >>> 1); i >= 0; i--) {
    56.       toBottom(arr, i, arr.length, comp);
    57.     }
    58.     for (let i = arr.length - 1; i > 0; i--) {
    59.       swap(arr, i, 0);
    60.       toBottom(arr, 0, i, comp);
    61.     }
    62.     arr.reverse();
    63.   }
    64. }