Mongoose find is not working with query object

Question

I am learning node.js with mongo db. I have a code to fetch records and that works fine

await studentModel.find({}, (err, data) => {
    if (err) throw err;
      students= data.map((d) => {
        return new InterviewQuestion(d['roll_no'], d['name']);
      });
    });

but when I want to filter them then the query doesn't return any record

await studentModel.find({sClass: sClass}, (err, data) => { //sClassis a field in document and also the name of variable
    if (err) throw err;
      students= data.map((d) => {
        return new InterviewQuestion(d['roll_no'], d['name']);
      });
    });

if you want to find main problem, you can add controller, route, schema to the question, and request — Mohammad Yaser Ahmadi
– Mohammad Yaser Ahmadi, Commented Jan 23, 2021 at 18:55

Mohammad Yaser Ahmadi · Accepted Answer · 2021-01-23 18:52:29Z

1

when you use async/await don't use callback and use try/catch in async/await approach so you can do like this

try {
  let data = await studentModel.find({});
  students = data.map((d) => {
    return new InterviewQuestion(d["roll_no"], d["name"]);
  });
} catch (err) {
  throw err;
}

try {
  let data = await studentModel.find({ sClass: sClass });
  students = data.map((d) => {
    return new InterviewQuestion(d["roll_no"], d["name"]);
  });
} catch (err) {
  throw err;
}

this query is correctly

await studentModel.find({ sClass: sClass })

also you can try this :

await studentModel.find({ sClass})

your issue from another thing, because I tested the queries every things is OK

answered Jan 23, 2021 at 18:52

Mohammad Yaser Ahmadi

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4 Comments

Imad Over a year ago

Why can't I used call back with async methods? I heard callback are best for handling asyn requests. Also my code without filter works.

Mohammad Yaser Ahmadi Over a year ago

where did you heard callback are best for handling async requests??

Imad Over a year ago

Everywhere, as an example w3schools.com/js/js_callback.asp

Mohammad Yaser Ahmadi Over a year ago

you can use async/await with try/catch togheter or a promise function without await with .then().catch() or a function with callback, there are 3 approach

Imad · Accepted Answer · 2021-01-23 11:08:04Z

0

I used a different name for the variable sClass and then it worked. I am still wondering why it is not allowed to have a filter variable with the same name as of document field.

answered Jan 23, 2021 at 11:08

Imad

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