Can't modify Mongoose data

Question

I have this code:

router.post('/BWreport', async function(req, res, next){
     try{
        var cname = await corporate.find().select('corporateID username');
        cname.forEach(function(cname, await){
          cname["totalcases"] = 1;
        });
        return res.json({ response:true, data:cname });
      }catch(err){
        return res.json({ response:false, data:err  });
      }
});

As you can see in the output, totalcases is not getting added:

    "response": true,
    "data": [
        {
            "_id": "61d3f90340b6cad5974ca50a",
            "username": "SB Demo",
            "corporateID": "SB00001"
        },
        {
            "_id": "62266f20fa0eb7a8fbe7d82a",
            "corporateID": "SB00002",
            "username": "NeoGrowth"
        }]

as you can see new key/value pair not getting in output, can anyone tell me why? desired output below

    "response": true,
    "data": [
        {
            "_id": "61d3f90340b6cad5974ca50a",
            "username": "SB Demo",
            "corporateID": "SB00001",
            "totalcases": "1"
        },
        {
            "_id": "62266f20fa0eb7a8fbe7d82a",
            "corporateID": "SB00002",
            "username": "NeoGrowth",
            "totalcases": "1"
        }]

First problem is that you are using a keyword as a variable name, and reusing a variable name `function(cname, await)` — Codebling, Nov 04 '22 at 07:14
@vighnesh153 `await` is a reserved keyword so that also needs to be changed — Codebling, Nov 04 '22 at 07:19
Not entirely https://stackoverflow.com/questions/55934490/why-are-await-and-async-valid-variable-names (though in the circumstances that it appears it definitely deserves to be refactored out) — CertainPerformance, Nov 04 '22 at 07:24
@CertainPerformance that is weird. As I was writing it, I thought to myself that it's weird that a new feature could introduce reserved words. Thanks for the correction. My statement was obviously wrong anyway since OP appeared to be using said code — Codebling, Nov 04 '22 at 07:26

score 2 · Accepted Answer · edited Nov 04 '22 at 07:21

2

Mongoose documents are immutable. Use .lean() to make it return a Javascript object that can be modified:

router.post('/BWreport', async function(req, res, next){
     try{
        var cname = await corporate.find().select('corporateID username').lean();

        cname.forEach(function(c, await){
          c["totalcases"] = 1;
        });

        return res.json({ response:true, data:cname });
        }catch(err){
        return res.json({ response:false, data:err  });
      }
});

edited Nov 04 '22 at 07:21

Codebling

10,764
2
38
66

answered Nov 04 '22 at 07:15

Drashti Kheni

1,065
9
23

2

lean() returns a JavaScript object instead of a Mongoose document. New key/value pair is not added because we can not modify mongoose document. – Drashti Kheni Nov 04 '22 at 07:19
yep waiting for timer to end – Ankit Patel Nov 04 '22 at 07:20

Syed Jawad · Answer 2 · 2022-11-04T07:31:34.810

1

router.post('/BWreport', async function(req, res, next){
 try{
    var cname = await corporate.find().select('corporateID username');
    cname.forEach((elem, ind, arr) => {
      arr[ind]['totalcases'] = 1;
    });
    return res.json({ response:true, data:cname });
  }catch(err){
    return res.json({ response:false, data:err  });
  }
});

edited Nov 04 '22 at 07:31

answered Nov 04 '22 at 07:27

Syed Jawad

51
6

you can't still edit it unless you add `lean()` method. – Stacks Queue Nov 04 '22 at 07:58

Can't modify Mongoose data

2 Answers2