从 Mongo Query 返回的数据的错误处理

Question

仍然是一个相对新手，但我正在使用门户网站让人们检查一个人是否是俱乐部的成员。我正在使用 mongodb 和 mongoose 来执行此操作，但是当输入不在数据库中的数字时，会返回错误“TypeError：无法读取未定义的属性'用户名'”，但我不确定如何要处理此错误，请参阅下面的代码：我知道有几种方法可以重构和整理我的代码，但这是我想知道的猫鼬错误处理。干杯？？？？

app.get('/checkmembership', function(req, res) {

    var jsonResponse = {};
    var returnArray =[];

    var dbArray,
        queryArray,
        resulta,
        resultb,
        resultc,
        resultd,
        resulte,
        resultf;

    console.log("before running compareDetails " + returnArray);

    User.find({username: req.query.memberIdQuery}, function(err, foundData) {

        if(err){
            console.log(err);
        } else {
            dbArray = [foundData[0].username, foundData[0].emailaddress, foundData[0].surname];
            console.log(dbArray);
            dbArray = dbArray.join('|').toLowerCase().split('|');
            console.log(dbArray);
            queryArray = [req.query.memberIdQuery, req.query.emailQuery, req.query.surnameQuery];
            console.log(queryArray);
            queryArray = queryArray.join('|').toLowerCase().split('|');
            console.log(queryArray);
            returnArray = compareDetails(queryArray, dbArray);
            resulta = returnArray[0];
            resultb = returnArray[1];
            resultc = returnArray[2];
            resultd = returnArray[3];
            resulte = returnArray[4];
            resultf = returnArray[5];
        }

        jsonResponse = { 
            set_attributes: 
            {
                resulta : resulta,
                resultb : resultb,
                resultc : resultc,
                resultd : resultd,
                resulte : resulte,
                resultf : resultf
            },
        };

        res.send(jsonResponse);
    });
});

Answer 1

你需要检查你得到的数组是否不为空：

您可以尝试以下方法：

app.get('/checkmembership', function(req, res) {
    var jsonResponse = {};
    var returnArray =[];
    var dbArray,
        queryArray,
        resulta,
        resultb,
        resultc,
        resultd,
        resulte,
        resultf;

    console.log("before running compareDetails " + returnArray);  
        User.find({username:req.query.memberIdQuery}, function(err, foundData){
            if(err){
               console.log(err);
           } else {

            if(foundData && foundData.length) {

            dbArray = [foundData[0].username,foundData[0].emailaddress,foundData[0].surname];
            console.log(dbArray);
            dbArray = dbArray.join('|').toLowerCase().split('|');
            console.log(dbArray);
            queryArray = [req.query.memberIdQuery,req.query.emailQuery,req.query.surnameQuery];
            console.log(queryArray);
            queryArray = queryArray.join('|').toLowerCase().split('|');
            console.log(queryArray);
            returnArray = compareDetails(queryArray, dbArray);
            resulta = returnArray[0];
            resultb = returnArray[1];
            resultc = returnArray[2];
            resultd = returnArray[3];
            resulte = returnArray[4];
            resultf = returnArray[5];


            jsonResponse = { 
                set_attributes: 
                  {
                      resulta : resulta,
                      resultb : resultb,
                      resultc : resultc,
                      resultd : resultd,
                      resulte : resulte,
                      resultf : resultf
                  },
                  };
                 res.send(jsonResponse);
                } else {
                    res.send("Empty result");
                }
           }
       });
});

Answer 2

当输入一个不在数据库中的数字时，返回错误“TypeError: Cannot read property 'username' of undefined”

这是因为默认情况下，当没有匹配记录时foundData 将是一个空数组[]。所以， foundData[0]，技术上将是undefined。

执行查询时，结果将是一个文档数组。

来源 mongoose docs

为避免此错误，您可以在访问 foundData 的第 0 个元素之前检查它的大小。

对您的代码进行这些更改。

app.get('/checkmembership', function (req, res) {

  let {memberIdQuery, emailQuery, surnameQuery} = req.query;

  User.find({
    username: memberIdQuery
  }, function (err, foundData) {

    if (err) {
      console.log(err);
      return res.status(500).send({
        msg: `memberIdQuery = ${memberIdQuery} doesnt exist`
      });
    }

    if (!foundData || foundData.length === 0) {
      return res.status(200).send({
        msg: `No records found for memberIdQuery = ${memberIdQuery}`
      });
    }

    let dbArray = [
      foundData[0].username,
      foundData[0].emailaddress,
      foundData[0].surname
    ];
    dbArray = dbArray.join('|').toLowerCase().split('|');

    let queryArray = [
      memberIdQuery,
      emailQuery,
      surnameQuery
    ];
    queryArray = queryArray.join('|').toLowerCase().split('|');

    let [resulta, resultb, resultc, resultd, resulte, resultf] = compareDetails(queryArray, dbArray);

    return res.send({
      set_attributes: {
        resulta: resulta,
        resultb: resultb,
        resultc: resultc,
        resultd: resultd,
        resulte: resulte,
        resultf: resultf
      },
    });

  });
});