在nedb中更新一行

Question

我在nedb中有以下数据。

["UserId":"1446943507761","UserName":"xxx","link":"xxx.html","taskDone":"false","id":14,"_id":"fdaaTWSxloQZdYlT"] 
["UserId":"1446943507761","UserName":"xxx","link":"xxx.html","taskDone":"false","id":1,"_id":"fzh2cedAXxT76GwB"] 
["UserId":"1446943507761","UserName":"xxx","link":"xxx.html","taskDone":"false","id":0,"_id":"k4loE7XR5gioQk54"] 

我想更新id为0的行，并将taskDone的值设置为true。我使用以下查询将值设置为true

db.taskmap.update({ _id: "k4loE7XR5gioQk54", UserName:"xxx" }, { $set: { taskDone: "true"} }, function (err, numReplaced) { 
    console.log("replaced---->" + numReplaced); 
    }); 

它更新值，但它更新为新行。它基本上插入一个具有相同值的新行，除了taskdone值为true。它不会删除现有数据。因此，在更新后的最终数据表中，我得到了id 0的两行，除了taskDone之外，所有值都相同。我不确定我是否做错了什么。如果有人能告诉我更新值的正确方法，这将会很有帮助。

Answer 1

update希望四个参数

var Datastore = require('nedb'); 
var db = new Datastore(); 

db.insert(
[ 
    { 
    "UserId":"1446943507761", 
    "UserName":"xxx", 
    "link":"xxx.html", 
    "taskDone":"false", 
    "id":14, 
    "_id":"fdaaTWSxloQZdYlT" 
    }, 
{ 
    "UserId":"1446943507761", 
    "UserName":"xxx", 
    "link":"xxx.html", 
    "taskDone":"false", 
    "id":1, 
    "_id":"fzh2cedAXxT76GwB" 
}, 
{ 
    "UserId":"1446943507761", 
    "UserName":"xxx", 
    "link":"xxx.html", 
    "taskDone":"false", 
    "id":0, 
    "_id":"k4loE7XR5gioQk54" 
    }], 
    function (err, newDocs) { 
    // empty here 
    } 
); 
db.update(
      { _id: "k4loE7XR5gioQk54", UserName:"xxx" }, 
      { $set: { taskDone: "true"} }, 
      {},// this argument was missing 
      function (err, numReplaced) { 
      console.log("replaced---->" + numReplaced); 
      } 
      ); 
// should give the correct result now 
db.find({}).exec(function (err, docs) {console.log(docs);});