Mongodb - find all documents which contain value in array using $regex operator

Looking to perform a search in my Mongo database which will find all documents that contain a certain string.

The first part of the code splits the user input by spaces, then pushes it to an array.

The second part of the code searches the database to find a match between each item in the array and the firstName field.

I'm trying to use the regex operator to ignore case sensitivity and also see if each element is contained anywhere in the field; i.e. the array element string "f", would yield a match for "frank", "doofus", but not "carlos" - etc.

Here is my code:

var string = 'carlos f sdf';
string = string.split(" ");
var stringArray = new Array();
for(var i =0; i < string.length; i++){
   stringArray.push(string[i]);
}

User.find({firstName: { $regex: {$in: stringArray}, $options: 'i'}}).select("-password").then(user=>console.log(user))

And this is the error I'm getting:

>UnhandledPromiseRejectionWarning: CastError: Cast to string failed for value "{ '$in': [ 'carlos', 'f', 'sdf' ] }" at path "firstName" for model "users"

Any ideas what am I doing wrong?

We can use or function for getting result

User.find({
    "$or": [{
        firstName: { $regex: 'carlos', $options: 'i'}
    }, 
   {
        firstName: { $regex: 'f', $options: 'i'}
    },
   {
        firstName: { $regex: 'sdf', $options: 'i'}
    }]
});

You can use '|' as an 'OR' operator for the regular expressions.

db.collection.find({ "firstName": { "$regex": "^carlos$|^f$|^sdf$", $options: "i" } })

The above query should work for you if you want to match the exact values.

If you want to match for those documents which contain given strings then use the below query.

db.collection.find({ "firstName": { "$regex": "carlos|f|sdf", $options: "i" } })

And as you asked about dynamic length input then you just have to Join all those string with '$|^' and once all the strings are joined you can append it with '$' and prepend it with '^' for the exact match in case of contain you just need to join all the string with '|' operator.

Thank you for the responses everyone. Below is how I solved the problem

var string = req.params.postParams
string = string.split(" ");
var stringArray = new Array();
for(var i =0; i < string.length; i++){
    stringArray.push(string[i]);
}
var regex = stringArray.map(function (e) { return new RegExp(e, "i"); });

User.find({firstName: { $in: regex }).select("-password").then(user=>console.log(user))