javascript - 变量未关闭(Variables not closing)

Question

I am trying to do a depth-first search (DFS) of a generic tree.

(我正在尝试对通用树进行深度优先搜索（DFS）。)

The goal for each node is to know its level AND the maximum number of levels beneath it.

(每个节点的目标是知道其级别及其下的最大级别。)

An example tree looks like:

(示例树如下所示：)

The DFS order should (I think) be: 1,2,3,5,6,7,4,8,9,10,11.

(DFS顺序应该是：1、2、3、5、6、7、4、8、9、10、11。)

What I am trying to achieve is: Node 1: Level 1, max levels beneath=4

(我正在尝试实现的是：节点1：级别1，最大级别低于= 4)

Node 2: Level 2, max levels beneath=3

(节点2：级别2，最大级别低于= 3)

Node 3: Level 3, max levels beneath=2

(节点3：级别3，最大级别低于= 2)

...

(...)

Node 9: Level 2, max levels beneath=1

(节点9：等级2，最大等级低于= 1)

I am, so far, able to properly count the levels and max levels, but whenever I try and save them to a new object, what ultimately results is the last level/max-level combination of numbers (in this example, it would be level=3, max-level beneath=0. I think it is not closing over the variables properly, but I must admit I can't figure out how to change it to make it work. I assume it must be some sort of closure, but I haven't been able to adapt the other Stack answers I've found on closures.

(到目前为止，我已经能够正确地计算级别和最大级别，但是每当我尝试将它们保存到新对象时，最终结果是数字的最后一个级别/最大级别组合（在本示例中，它将是级别= 3，最大级别低于=0。我认为它没有正确关闭变量，但我必须承认我不知道如何更改它以使其起作用，我认为它必须是某种形式的闭合，但是我无法适应在闭包上找到的其他Stack答案。)

 var groupIDInfo={
 BASE:[1], 1:[2,8,9], 2:[3,4], 3:[5], 4:[], 5:[6,7], 6:[], 7:[], 8:[],
  9:[10,11], 10:[], 11:[]}
var levelInfo={};
var level=0;
var longestPath=0;
var levelAndPath=[];

function detLevels(groupIDInfo, parent){

  if(!(parent in groupIDInfo)){
    console.log("parent not in array");
    return;
  }
  groupIDInfo[parent].forEach(function (child){
    level++;
    if (level>longestPath){
      longestPath=level;      
    }
    levelAndPath[0]=level;
    levelAndPath[1]=longestPath;
    levelInfo[child]=levelAndPath;

    detLevels(groupIDInfo, child);

    level--;
    //set parent longest path
    longestPath=level;
    levelInfo[parent]=levelAndPath;

  });
}
detLevels(groupIDInfo, "BASE");

  ask by robert smith translate from so

Answer 1

You're using a single array levelAndPath , and pushing references to it into levelInfo , as opposed to pushing different arrays.

(您正在使用单个数组levelAndPath ，并将对它的引用推送到levelInfo ，而不是推送不同的数组。)

(I haven't looked if there are any other errors beyond that, but this one is easily fixable by moving var levelAndPath=[]; inside forEach .)

(（我没有查看是否有其他错误，但是可以通过在forEach内移动var levelAndPath=[];来轻松解决此错误。）)

It is not about closures.

(它与闭包无关。)

It is the fact that levelInfo[parent]=levelAndPath;

(实际上是levelInfo[parent]=levelAndPath;)

doesn't copy levelAndPath - it just sticks in a reference.

(不复制levelAndPath只是levelAndPath在参考中。)

Here's a snazzy demo, thanks to the advances in Stack Overflow snippets:

(这是一个令人眼花demo乱的演示，这要归功于Stack Overflow片段的进步：)

 let a = [1, 2, 3]; let b = [a, a, a]; a[2] = 4; console.log(JSON.stringify(b)); // Huh? [[1,2,4],[1,2,4],[1,2,4]]?!? console.log(b); // Here's what _really_ happened...