How can I return only the string value of an object from a MongoDB array

Question

valueOf() returns this:

[
   {},
   { toUser: '5ed9d49c7e516616600eb693' },       
   { toUser: '5ed9d49c7e516616600eb693' },       
   { toUser: '5ed9d49c7e516616600eb693' },       
   { toUser: '5ed9d3897e516616600eb692' }        
]

I want to return only the value like "5ed9d3897e516616600eb692" or whatever toUser has. How?

could you show us the full code?

Ilijanovic
– Ilijanovic

2020-06-08 11:12:32 +00:00
Commented Jun 8, 2020 at 11:12 — Ilijanovic
– Ilijanovic, Commented Jun 8, 2020 at 11:12
do you need array of id strings instead of array of object?

Rajneesh
– Rajneesh

2020-06-08 11:15:41 +00:00
Commented Jun 8, 2020 at 11:15 — Rajneesh
– Rajneesh, Commented Jun 8, 2020 at 11:15

Tom Slabbaert · Accepted Answer · 2020-06-08 11:19:27Z

2

This can be done in a couple of different ways, the best of which is using distinct:

db.collection.distinct("toUser")

Output will be:

[
    '5ed9d49c7e516616600eb693',
    '5ed9d49c7e516616600eb693',
    '5ed9d49c7e516616600eb693',
    '5ed9d3897e516616600eb692'
]

answered Jun 8, 2020 at 11:19

Tom Slabbaert

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Comments

brk · Accepted Answer · 2020-06-08 11:17:04Z

1

You can use reduce and inside callback check if the object has any key using Object.keys and length. If it has k then push the value using Object.values into the accumulator array

let data = [{},
  {
    toUser: '5ed9d49c7e516616600eb693'
  },
  {
    toUser: '5ed9d49c7e516616600eb693'
  },
  {
    toUser: '5ed9d49c7e516616600eb693'
  },
  {
    toUser: '5ed9d3897e516616600eb692'
  }
];
let filterdValue = data.reduce((acc, curr) => {
  const objKey = Object.keys(curr);
  if (objKey.length > 0) {
    acc.push(...Object.values(curr))
  }
  return acc;
}, []);
console.log(filterdValue)

answered Jun 8, 2020 at 11:17

brk

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Comments

shiva · Accepted Answer · 2020-06-08 11:19:04Z

0

You can use following query to convert object to string

> db.objectidToStringDemo.aggregate([{$project: {toUser: {$toString: "$toUser"}}}]);

answered Jun 8, 2020 at 11:19

shiva

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