为什么push()无效?

我正在编辑一个json文件节点.JS,但我被困在这一部分:

 var filterlist = require('./censor.json');
        var fs = require('fs');
        var addWord = req.body.addBlacklist;
        addWord = addWord.trim();
        addWord = addWord.toLowerCase();
        var findWord = false;
        for(var i = 0; i < filterlist.Words.length; i++) {
            if(filterlist.Words[i] == addWord) {
                findWord = true;
            }
        }
        if(findWord == false) {
            filterlist.Words.push(addWord);
            ...

即使push()是一个函数,我得到的只是

TypeError: filterlist.Words.push is not a function

{"Words":{},"Phrases":{},"Whitelist":{}}

我不知道为什么。有人能告诉我我做错了什么吗?