Nodejs,mongodb - using $nin or $in for object ids or _id
The way $nin works in mongo is that it takes an array of values to check.
The code:var string = a+","+b Doesnt make this a valid array. as you're creating a string with the value sdfsdznfsdz, u89tgngnfdb
So $nin is treating the array as that value, not the way you're trying to implement.
Solution to do what you want is to create an array with those values.
So something like:
var ids = new Array( new ObjectId("1124edcef241"), new ObjectId("56943decfeca845") );// Dont put [ ] as a parameter. Just send a variable thats an array Model.find( {_id : { $nin : ids } } ); ...Just incase you're a tad hazy regarding arrays, I suggest having a read of this: