How can I find all documents where a field contains a particular string?

Question

I'm new to mongodb and mongoose and I'm trying to figure out how to do a query that let's me find all records/documents where a field contains a particular string. This is for use with a search feature. For example, if I have a "users" collection, then I want to find all users whose firstname begins with, say, the string "Jo". Like this:

var Users = require('./models/users');
Users.find({ firstname : contains the string 'Jo' }, function(err, user) {
    if (err) {
            return done(err);
    } else {
        return res.json({
            firstname: user.firstname,
        });
    }
});

I'm not sure what to put in place of "contains the string 'Jo'" so that this query will work. Basically, it should return records/documents such as "Joe", "John", "Joyce", etc.

UPDATE===========================================

Here is the updated code, but it returns all records, instead of only returning the ones that match "str":

app.get('/search/:str', function(req, res) {
    var Users = require('./models/users');
    Users.find({name: /[req.params.str]/}, function(err, data) {
        if (err) return console.error(err);
        return res.json(data);
    })
});

The problem is with /[req.params.str]/. If str is set to "Jo", then it should only return users whose name contains the string "Jo", but it is returning every record. How can I fix this?

Answer 1

2 ways to do this:
With regular expression. MongoDB supports regular expression match. here's an example:

users.find({firstname: /Jo/}, function(err, doc) {...})

However, if you got a big collection, it's going to be slow. Because regular expression usually doesn't use index at all unless you have a fixed prefix like /^Jo/.

Or in some situations you may want to try the new feature, full text search: First of all, you need an text index:

db.users.ensureIndex( { firstname: "text" } );

Then use the $text operator:

db.users.find({ $text: { $search: "Jo"}});

The text search does not just look for exactly what you are searching. And in some situations it may not work the way you wanted.

The $text operator can search for words and phrases. The query matches on the complete stemmed words. For example, if a document field contains the word blueberry, a search on the term blue will not match the document.

More information, please refer to the document.