Minimum Priority Queue ES6 Class syntax.

MinPQ-es6.js

class MinPQ {
  constructor(comparator) {
    this.comparator = comparator || MinPQ.compare;
    this.items = [];
    this.n = 0;
  }

  insert(value) {
    this.items[++this.n] = value;
    this.swim(this.n);
  }

  isEmpty() { return this.n === 0; }

  size() { return this.n; }

  less(a, b) { return this.comparator(this.items[a], this.items[b]) < 0; }

  greater(a, b) { return this.comparator(this.items[a], this.items[b]) > 0; }

  exch(a, b) {
    let x = this.items[a];
    this.items[a] = this.items[b];
    this.items[b] = x;
  }

  popMin() {
    if(this.isEmpty()) { throw new Error('No Items on Priority Queue'); }
    this.exch(1, this.n);
    let min = this.items[this.n--];
    this.sink(1);
    return min;
  }

  min() {
    return this.items[1];
  }

  swim(k) {
    while(k > 1 && this.greater(Math.floor(k/2), k)) {
      this.exch(k, Math.floor(k/2));
      k = Math.floor(k/2);
    }
  }

  sink(k) {
    while(2*k <= this.n) {
      let k2 = 2*k;
      if(k2 < this.n && this.greater(k2, k2+1)) { k2++; }
      if(!this.greater(k, k2)) { break; }
      this.exch(k, k2);
      k = k2;
    }
  }
  
  static compare(valA, valB) {
    if(valA > valB)   { return 1;  }
    if(valA === valB) { return 0;  }
    if(valA < valB)   { return -1; }
  }  
}