For this document: { "_id" : 3, "name" : " Shyam Lingam " }

Expected: while retrieving _id = 3 then result should come like below:

{ "_id" : 3, "name" : "Shyam Lingam" }

I tried this: db.collection.find({_id:3},{name:{$trim:{input:"$name"}}})

{ "_id" : 3, "name" : "Shyam Lingam" }

but still whitespace between Shyam and Lingam is there which should not come.

>Solution :

This query may look complex.

1. $trim – Trim the value of 1.1 at the beginning and end.

   1.1. $reduce – Transform array to string.

   1.1.1. input – Split name by space and filter the word which is not space.

   1.1.2. initialValue – Set the initial value as an empty string.

   1.1.3. in – With $concat, combine all the elements into a string with ‘ ‘ as the delimiter.

db.collection.find({
  _id: 3
},
{
  name: {
    $trim: {
      input: {
        $reduce: {
          input: {
            $filter: {
              input: {
                $split: [
                  "$name",
                  " "
                ]
              },
              cond: {
                $ne: [
                  "$$this",
                  ""
                ]
              }
            }
          },
          initialValue: "",
          in: {
            $concat: [
              "$$value",
              " ",
              "$$this"
            ]
          }
        }
      }
    }
  }
})

Demo @ Mongo Playground