在Javascrip中形成trie对象

Question

所以，我试着做一个trie，把句子中的单词联系起来，而不是单词的前缀。我已经在Python中做到了这一点，如下所示：

#statement trie

class strie (object):

def __init__(self):
    self.trie = {}
def __repr__(self):
    return str(self.trie)
def __str__(self):
    return str(self.trie)
def statement(self, phrase):
    words = phrase.split()
    current = self.trie
    while len(words) > 0:
        word = words.pop(0)
        if word in current.keys():
            current = current[word]
        else:
            current[word] = {}
            current = current[word]

我会通过测试得到结果：

       r
=> {'The': {'apple': {'is': {'red': {}, 'blue': {'or': {'yellow': {}}}}}}}

然而，当我用javascript几乎完全相同地实现这一点时，一些奇怪的事情发生了。下面是我用javascript实现的：

    //constructs a trie formed form a single sentence as an object.
function single_trie(phrase) {
    phrase = phrase.toLowerCase();
    var trie = {};
    var words = phrase.split(" ");
    var current = trie;
    while (words.length > 0) {
        var word = words.shift();
        if(word in current) current = current[word];
        else {
            current[word] = {};
            current = current[word];
        }
    }
    return trie;
}

我得到了一个非常奇怪的结果：

    var strie = single_trie("the apple is red and blue");
console.log(strie);

{ the: { apple: { is: [Object] } } }

是什么导致我的javascript实现出现这种情况？为什么它显示[对象]？如何让它像python实现一样工作？你知道吗