使用参考对象的JavaScript中的BST

Question

I found this algorithm from Data structures and algorithms in javascript. For the insertion method, there are two references to the root (current and parent). My question is, why can't i change both current and parent to this.root? They both point to this.root. The code does not work properly when I do that however

'use strict';

var BST = function() {
  this.root = null;

//embed _Node inside BST so it comes with when BST is created
  this._Node = function(data, left, right) {
    this.data = data;
    this.count = 1;
    this.left = left;
    this.right = right;
  };

  this._Node.prototype.show = function() {
    return this.data;
  };

  this._Node.prototype.showCount = function() {
    return this.count;
  }
};


BST.prototype.insert = function(data) {
  //use this data for a new node
  var n = new this._Node(data, null, null);
  //if root is null, put this new node and its data into root
  if (this.root === null) {
    this.root = n;
  }
  else {
    //find a child position for this node
    var current = this.root;
    var parent;
    while (true) {
      parent = current;
      if (data < current.data) {
        current = current.left;
        if (current === null) {
          parent.left = n;
          break;
        }
      }
      else {
        current = current.right;
        if (current === null) {
          parent.right = n;
          break;
        }
      }
    }
  }
};

var nums = new BST(); 
nums.insert(23); 
nums.insert(45); 
nums.insert(16); 
nums.insert(37); 
nums.insert(3); 
nums.insert(99); 
nums.insert(22); 

Answer 1

current does not refer to this.root throughout the entire algorithm.

It is initialized as this.root , but then it is quickly reassigned to either current = current.left; or current = current.right; . From that moment on current is no longer this.root . It is either this.root.left or this.root.right .

On the next iteration of the while loop it will get reassigned again, but it will never be this.root again, since it is alway being reassigned to a child node of current .

parent is similar, being this.root only on the first iteration. On each subsequent iteration it is reassigned by parent = current; and since current is no longer this.root , parent won't be this.root` either.

Answer 2

parent仅用于保留上一个节点的参考，创建新节点n ，然后在树中找到它的位置，当current变为null ，找到节点n的目标位置，则需要将其分配为child（ left或right ）到parent节点