JavaScript 与 python : Different output for a function with two recursion branches

Question

我一直在将 python 代码翻译为 javascript，没有任何问题，但对于下面的示例，我未能这样做，并且不知道原因是什么。尽管代码相似，但 javascript 代码似乎产生了与 python 完全不同的输出。我已经调查了这个问题，看来 javascript 没有执行第二个递归分支？有人知道如何使 javascript 代码输出类似于 python 的输出吗？谢谢

1-Python代码:

def createNode(_id, right, left):
    return {'id': _id, 'left': left, 'right': right}

n1 = createNode(1, None, None)
n2 = createNode(2, None, None)
n3 = createNode(3, None, None)
n4 = createNode(4, None, None)
n5 = createNode(1, n1, n2)
n6 = createNode(2, n3, n4)
n7 = createNode(3, n5, n6)

def DownTree(lst, node): 
    left = node['left']
    right = node['right'] 

    if(right == None):
        lst.append(node['id'])
    else:
        DownTree(lst, right)    
    if(left == None):
        lst.append(node['id'])
    else:
        print('will excute')
        DownTree(lst, left)


lst = []
DownTree(lst, n7)

print(lst)
## outputs: [1, 1, 2, 2, 3, 3, 4, 4]

2- JavaScript 代码:

function createNode(_id, right, left){
    return {'id': _id, 'left': left, 'right': right}
}
n1 = createNode(1, undefined, undefined)
n2 = createNode(2, undefined, undefined)
n3 = createNode(3, undefined, undefined)
n4 = createNode(4, undefined, undefined)
n5 = createNode(1, n1, n2)
n6 = createNode(2, n3, n4)
n7 = createNode(3, n5, n6)

function DownTree(lst, node){ 
  left = node['left']
  right = node['right'] 

  if(right == undefined){
    lst.push(node['id'])
  }
  else{
    DownTree(lst, right)
  }  
  if(left == undefined){
    lst.push(node['id'])
  }
  else{
    console.log('not executed!')
    DownTree(lst, left)
  }
} 

lst = []
DownTree(lst, n7)
console.log(lst)
// outputs: [1, 1, 1, 3]

Answer 1

在您的 JS left 和 right 中，范围不正确。您需要将 var 或 let 添加到它们的定义中，以便它们不是全局的

var left = node['left']
var right = node['right']