how to update data in mongodb using angular nodejs express

Question

I want to update the likes' value with 1.

My MongoDB structure is as follows .

   {"_id":{"$oid":"5f980a66c4b0d52950bdf907"},
    "course_id":"5002",
    "lecture_id":"451",
    "__v":0,
    "created_at":{"$date":"2020-10-27T11:54:14.842Z"},
    "message":[
    {
    "_id":{"$oid":"5f980a84c4b0d52950bdf90a"},
    "from":{
    "userId":"68819","name":"Developer IIRS",
    "avatar":"https://api.adorable.io/avatars/285/811753.png"
    },
    "content":"ok",
    "likes":0,
    "parent_id":null,
    "created_at":{"$date":"2020-10-27T11:54:44.388Z"}
    }
    ]
    }

Here is my code to update value of likes

    router.post('/:lectureId/:courseId/:id', function(req, res, next) {
      let query = {
        lecture_id: req.params.lectureId,
        course_id: req.params.courseId
    
      };
      let update = { $push: { message: { _id: req.params.id,likes: 1 } } }
    
      var options = {
        new: true
      }
      console.log('Liked', query)
    
      Chat.update(query, update, function(err, result) {
        if (err) {
          //res.send(err);
          console.log('err',err );
          return err;
        }
        res.json(result);
      })
    });

Its basically adding new document. I am stuck here how can i do this.

Solution with Ankit · Accepted Answer · 2020-10-28 06:22:53Z

1

  "lecture_id": "451",
  "course_id": "5002"
},
{
  $inc: {
    "message.$[elem].likes": 1
  }
},
{
  new: true,
  arrayFilters: [
    {
      "elem._id": "5f980a84c4b0d52950bdf90a"
    }
  ]
})```

answered Oct 28, 2020 at 6:22

Solution with Ankit

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Comments

wak786 · Accepted Answer · 2020-10-28 06:27:28Z

0

Here is the mongo query.

db.collection.update({
  "lecture_id": "451",
  "course_id": "5002",
  "message._id": "5f980a84c4b0d52950bdf91a"
},
{
  "$inc": {
    "message.$.likes": 1
  }
})

Try it here Mongo Playground

Not an expert in nodejs. Below update statement may work for you.

let update = { $inc: { "message.$.likes": 1 } }

edited Oct 28, 2020 at 6:27

answered Oct 27, 2020 at 13:26

wak786

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7 Comments

Solution with Ankit Over a year ago

Thanx @wak786 its working as you said but its not what i am looking for. this is adding likes : 1 in every element of message array. but i want to update by adding 1 in likes value with respect to message._id. basically i have like button in my application and when i hit like button with respect to the message it should addon 1 in likes : 1 or like:2 and so on. with respect to the message id. not to all messages .

Solution with Ankit Over a year ago

woohaaa ! finally its working for me . thanx @wak786 a lot your answer give me adirection. The following works for me. ` let update = { $inc: { "message.$[elem].likes" :1 } } var options = { new: true, arrayFilters: [ { "elem._id": req.params.id } ] }`

wak786 Over a year ago

Cool.. Posted an update to answer. Also just saw your answer too. Looks good.

Solution with Ankit Over a year ago

ya thats also looks good. now i am curious about which solution is better performance wise. bcz i am so new in Mongo so pleas suggest. is my query correct. is it the right way to do the same. ? @wak786

wak786 Over a year ago

your query is correct. Only thing different is, in my query update operation already knows which object to update based on filter. In yours it only gets to know that after checking in arrayFilters. Both should work fine in normal workload. I am not not 100% sure but mine can be more performant if you have proper index.

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