javascript 控制台未返回预期结果

Question

我正在尝试学习图数据结构，并通过控制台当前数据发现了这种奇怪的行为，我的主要代码如下

class Graph {
  constructor() {
    this.adjacencyList = {};
  }

  addVertex(vertex) {
    if (!this.adjacencyList[vertex]) this.adjacencyList[vertex] = [];
  }

  addEdge(v1, v2) {
    this.adjacencyList[v1].push(v2);
    this.adjacencyList[v2].push(v1);
  }

  removeEdge(v1, v2) {
    this.adjacencyList[v1] = this.adjacencyList[v1].filter((el) => el !== v2);
    this.adjacencyList[v2] = this.adjacencyList[v2].filter((el) => el !== v1);
  }
}

我的控制台日志是

let graph = new Graph();
graph.addVertex("tokyo");
graph.addVertex("dallas");
graph.addVertex("aspen");

graph.addEdge("tokyo", "dallas");
graph.addEdge("dallas", "aspen");

console.log(graph.adjacencyList);

graph.removeEdge("dallas", "tokyo");

console.log(graph.adjacencyList);

我通常期望的是删除之前的第一个console.log应该包含边缘，而之后的console.log将包含删除后的边缘，这就是我在对象中看到的

{东京：数组(1)，达拉斯：数组(2)，白杨：数组(1)}

{东京：数组(0)，达拉斯：数组(1)，白杨：数组(1)}

但是当我打开对象时，我没有看到对象 1 中的预期值

aspen: ['dallas']
dallas: ['aspen']
Tokyo: []

这与 console.log 中的第二个对象完全相同

Answer 1

在记录对象之前，创建它的克隆：

structuredClone(graph.adjacencyList)

这样，在记录相邻的“列表”时，引用就是一个新对象。

class Graph {
  constructor() {
    this.adjacencyList = {};
  }
  addVertex(vertex) {
    if (!this.adjacencyList[vertex]) this.adjacencyList[vertex] = [];
  }
  addEdge(v1, v2) {
    this.adjacencyList[v1].push(v2);
    this.adjacencyList[v2].push(v1);
  }
  removeEdge(v1, v2) {
    this.adjacencyList[v1] = this.adjacencyList[v1].filter((el) => el !== v2);
    this.adjacencyList[v2] = this.adjacencyList[v2].filter((el) => el !== v1);
  }
}

let graph = new Graph();
graph.addVertex("tokyo");
graph.addVertex("dallas");
graph.addVertex("aspen");

graph.addEdge("tokyo", "dallas");
graph.addEdge("dallas", "aspen");

console.log(structuredClone(graph.adjacencyList));

graph.removeEdge("dallas", "tokyo");

console.log(structuredClone(graph.adjacencyList));

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