NodeJS Express create Mongoose query from string

Question

I have this string:

var filter = '{stamps:{$gte: 2020-11-06 06:42:25.000+01:00, $lte: 2020-11-06 09:52:25.000+01:00}'

Somehow I have to query mongoDB collection with this string.

Message.find(filter, function(err, messages){
  if(err){
    console.log(err);
  }else{
    //do something here
  }
})

Of course I am getting this error:

ObjectParameterError: Parameter "filter" to find() must be an object, got {stamps:{$gte: 2020-11-06 06:42:25.000+01:00, $lte: 2020-11-06 09:52:25.000+01:00}

is there some way to cast this string to object that will be acceptable to mongoDB?

after JSON.parse(filter) i am getting this error - SyntaxError: Unexpected token s in JSON at position 1 at JSON.parse (<anonymous>) — Vladimir Sarac
– Vladimir Sarac, Commented Nov 24, 2020 at 15:22

Benno · Accepted Answer · 2020-11-24 18:10:54Z

1

You could either change the way you construct your query, to pass it as JSON an then use JSON.parse() / JSON.stringify()

// Note the necessary double quotes around the keys
const jsonFilter = '{ "stamps": { "$gte": "2020-11-06 06:42:25.000+01:00", "$lte": "2020-11-06 09:52:25.000+01:00" } }'
const query = JSON.parse(jsonFilter)
Message.find(query, callback)

Or you could introduce another dependency like mongodb-query-parser that can parse the string for you.

const parser = require('mongodb-query-parser')
// Note it still needs double quotes around the dates to run properly
const filter = '{stamps:{$gte: "2020-11-06 06:42:25.000+01:00", $lte: "2020-11-06 09:52:25.000+01:00" } }'
const query = parser(filter)
Message.find(query, callback)

https://runkit.com/5fbd473b95d0a9001a2359b3/5fbd473b98492c001a8bba06

If you can't include the quotes around the values in the string, you can use a regular expression to add them. But keep in mind that this regex is tailored to match this exact date format. If the format can change or you want to also match other data types, you should try to include them in your filter string from the start.

const parser = require("mongodb-query-parser")
const filter = '{stamps:{$gte: 2020-11-06 06:42:25.000+01:00, $lte: 2020-11-06 09:52:25.000+01:00} }'
const filterWithQuotedDates = filter.replace(/(\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}\.\d{3}(\+\d{2}:\d{2})?)/g, '"$1"')
parser(filterWithQuotedDates)
Message.find(query, callback)

https://runkit.com/5fbd494bcd812c0019b491fb/5fbd4951ebe43f001a5b590a

It should be noted that a common use-case is to pass a MongoDB query via URL params and that there are special packages for that:

edited Nov 24, 2020 at 18:10

answered Nov 24, 2020 at 15:12

Benno

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5 Comments

Vladimir Sarac Over a year ago

i tried mongodb-query-parser but i am getting this error - SyntaxError: Unexpected token (1:27)

Richard Rublev Over a year ago

@Benno I am also getting the same error,can you reproduce the code?

Benno Over a year ago

@VladimirSarac the problem is the missing quotes around the dates. Do you have the possibility to include them? Otherwise they can be added e.g. via a Regex.. runkit.com/5fbd473b95d0a9001a2359b3/5fbd473b98492c001a8bba06

Benno Over a year ago

@RichardRublev here's a version that adds quotes around the dates with a simple regular expression runkit.com/5fbd494bcd812c0019b491fb/5fbd4951ebe43f001a5b590a

Benno Over a year ago

@VladimirSarac Glad I could help. Please consider marking my answer as accepted if it solved your problem

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