lib: refactor PriorityQueue to use private field

PR-URL: nodejs#43889
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Mestery <mestery@protonmail.com>

lib/internal/priority_queue.js

@@ -2,38 +2,30 @@
 
 const {
   Array,
-  Symbol,
 } = primordials;
 
-const kCompare = Symbol('compare');
-const kHeap = Symbol('heap');
-const kSetPosition = Symbol('setPosition');
-const kSize = Symbol('size');
-
 // The PriorityQueue is a basic implementation of a binary heap that accepts
 // a custom sorting function via its constructor. This function is passed
 // the two nodes to compare, similar to the native Array#sort. Crucially
 // this enables priority queues that are based on a comparison of more than
 // just a single criteria.
 
 module.exports = class PriorityQueue {
+  #compare = (a, b) => a - b;
+  #heap = new Array(64);
+  #setPosition;
+  #size = 0;
+
   constructor(comparator, setPosition) {
     if (comparator !== undefined)
-      this[kCompare] = comparator;
+      this.#compare = comparator;
     if (setPosition !== undefined)
-      this[kSetPosition] = setPosition;
-
-    this[kHeap] = new Array(64);
-    this[kSize] = 0;
-  }
-
-  [kCompare](a, b) {
-    return a - b;
+      this.#setPosition = setPosition;
   }
 
   insert(value) {
-    const heap = this[kHeap];
-    const pos = ++this[kSize];
+    const heap = this.#heap;
+    const pos = ++this.#size;
     heap[pos] = value;
 
     if (heap.length === pos)
@@ -43,14 +35,14 @@ module.exports = class PriorityQueue {
   }
 
   peek() {
-    return this[kHeap][1];
+    return this.#heap[1];
   }
 
   percolateDown(pos) {
-    const compare = this[kCompare];
-    const setPosition = this[kSetPosition];
-    const heap = this[kHeap];
-    const size = this[kSize];
+    const compare = this.#compare;
+    const setPosition = this.#setPosition;
+    const heap = this.#heap;
+    const size = this.#size;
     const item = heap[pos];
 
     while (pos * 2 <= size) {
@@ -71,9 +63,9 @@ module.exports = class PriorityQueue {
   }
 
   percolateUp(pos) {
-    const heap = this[kHeap];
-    const compare = this[kCompare];
-    const setPosition = this[kSetPosition];
+    const heap = this.#heap;
+    const compare = this.#compare;
+    const setPosition = this.#setPosition;
     const item = heap[pos];
 
     while (pos > 1) {
@@ -91,21 +83,21 @@ module.exports = class PriorityQueue {
   }
 
   removeAt(pos) {
-    const heap = this[kHeap];
-    const size = --this[kSize];
+    const heap = this.#heap;
+    const size = --this.#size;
     heap[pos] = heap[size + 1];
     heap[size + 1] = undefined;
 
     if (size > 0 && pos <= size) {
-      if (pos > 1 && this[kCompare](heap[pos / 2 | 0], heap[pos]) > 0)
+      if (pos > 1 && this.#compare(heap[pos / 2 | 0], heap[pos]) > 0)
         this.percolateUp(pos);
       else
         this.percolateDown(pos);
     }
   }
 
   shift() {
-    const heap = this[kHeap];
+    const heap = this.#heap;
     const value = heap[1];
     if (value === undefined)
       return;