node.js - 在服务器自身解决的路径错误中，为值 "NaN"转换为数字失败

Question

我是 Nodejs 的初学者，我不确定我能在这里问这么简单的事情。当我建立一个 Node 服务器连接到mongodb时，得到了这个错误:

Cast to Number failed for value "NaN" at path "count"

但是，错误在几分钟后消失了，服务器以某种方式再次运行，并且插入了计数模式。

我找不到让它再次运行的东西。我只是假设我的 Node 服务器无法获取值，因为“计数”模式消失了。

但是你能帮我用更好的方式思考吗？

这是我之前遇到的错误。

• 首先，当我检查 mongodb 中的数据收集时，没有“计数”模式。

> db.datas.find()
{ "_id" : ObjectId("5cb39eca6e5e3971fa934a2d"), "name" : "myData", "__v" : 0 }

• 其次， Node 服务器控制台向我显示以下错误:

Data ERROR: save:  { ValidationError: data validation failed: count: Cast to Number failed for value "NaN" at path "count"
    at ValidationError.inspect (/home/gkh/Desktop/Dev/myapp/node_modules/mongoose/lib/error/validation.js:59:24)
    at formatValue (util.js:430:38)
    at inspect (util.js:324:10)
    at format (util.js:253:18)
    at Console.log (console.js:130:21)
    at /home/gkh/Desktop/Dev/myapp/app.js:46:30
    at /home/gkh/Desktop/Dev/myapp/node_modules/mongoose/lib/model.js:4675:16
    at /home/gkh/Desktop/Dev/myapp/node_modules/mongoose/lib/utils.js:255:11
    at $__save.error (/home/gkh/Desktop/Dev/myapp/node_modules/mongoose/lib/model.js:471:16)
    at /home/gkh/Desktop/Dev/myapp/node_modules/kareem/index.js:246:48
    at next (/home/gkh/Desktop/Dev/myapp/node_modules/kareem/index.js:167:27)
    at next (/home/gkh/Desktop/Dev/myapp/node_modules/kareem/index.js:169:9)
    at Kareem.execPost (/home/gkh/Desktop/Dev/myapp/node_modules/kareem/index.js:217:3)
    at _handleWrapError (/home/gkh/Desktop/Dev/myapp/node_modules/kareem/index.js:245:21)
    at /home/gkh/Desktop/Dev/myapp/node_modules/kareem/index.js:272:14
    at _next (/home/gkh/Desktop/Dev/myapp/node_modules/kareem/index.js:94:14)
  errors: 
   { count: 
      { CastError: Cast to Number failed for value "NaN" at path "count"
    at new CastError (/home/gkh/Desktop/Dev/myapp/node_modules/mongoose/lib/error/cast.js:29:11)
    at model.$set (/home/gkh/Desktop/Dev/myapp/node_modules/mongoose/lib/document.js:1073:7)
    at model.set [as count] (/home/gkh/Desktop/Dev/myapp/node_modules/mongoose/lib/helpers/document/compile.js:140:26)
    at /home/gkh/Desktop/Dev/myapp/app.js:44:15
    at /home/gkh/Desktop/Dev/myapp/node_modules/mongoose/lib/model.js:4675:16
    at /home/gkh/Desktop/Dev/myapp/node_modules/mongoose/lib/query.js:4184:12
    at process.nextTick (/home/gkh/Desktop/Dev/myapp/node_modules/mongoose/lib/query.js:2741:28)
    at _combinedTickCallback (internal/process/next_tick.js:131:7)
    at process._tickCallback (internal/process/next_tick.js:180:9)
        message: 'Cast to Number failed for value "NaN" at path "count"',
        name: 'CastError',
        stringValue: '"NaN"',
        kind: 'Number',
        value: NaN,
        path: 'count',
        reason: [Object] } },
  _message: 'data validation failed',
  name: 'ValidationError' }

• 这是 app.js 文件的一部分:

mongoose.connect("mongodb://localhost:27017/user-node");
var mongod = mongoose.connection;
mongod.once("open", function(){
  console.log("DB connected!");
});
mongod.on("err", function(err){
  console.log("DB err: ", err);
});

var dataSchema = mongoose.Schema({
  name:String,
  count:Number
});

var Data = mongoose.model('data', dataSchema);
Data.findOne({name:"myData"}, function(err, data){
  if(err) return console.log("Data ERROR: ", err);
  if(!data){
    Data.create({name:"myData",count:0}, function(err, data){
      if(err) return console.log("Data ERROR", err);
      console.log("Counter initialized: ", data);
    });
  }
});

app.set("view engine", 'ejs');
app.use(express.static(path.join(__dirname + '/public')));

// callback function list
// render to firstPage.ejs page with params or non-params
app.get('/', function(req, res){
  Data.findOne({name:"myData"}, function(err, data){
    if(err) return console.log("Data ERROR : /path: ", err);
    data.count++;
    data.save(function(err){
      if(err) return console.log("Data ERROR: save: ", err);
      res.render('firstPage', data);
    });
  });
});
// set count to 0
app.get('/reset', function(req, res){
  setCounter(res, 0);
});
// check arg in req.query.count
app.get('/set/count', function(req, res){
  if(req.query.count) setCounter(res, req.query.count);
  else getCounter(res);
});
// placeholder : num
// any arg can place in num param
app.get('/set/:num', function(req, res){
  if(req.params.num) setCounter(res, req.params.num);
  else getCounter(res);
});

function setCounter(res, num){
  console.log("...setCounter...");
  Data.findOne({name:"myData"}, function(err, data){
    if(err) return console.log("Data ERROR: ", err);
    data.count=num;
    data.save(function(err){
      if(err) return console.log("Data ERROR: ", err);
      res.render('firstPage', data);
    });
  });
}

function getCounter(res){
  console.log("...getCounter...");
  Data.findOne({name:"myData"}, function(err, data){
    if(err) return console.log("Data ERROR", err);
    res.render('firstPage', data);
  });
}

如果我错了或者我的代码有错，请大家指教。提前致谢!

Answer 1

在进行任何操作之前，在该字段上设置一个默认值 0。出现此错误是因为没有为字段分配初始值。