Programmatically build dynamic query with Mongoose

Question

I'm trying to build a search from input received from a form.

router.get('/data', function(req, res) {
    var firstName=req.body.firstName,
    lastName=req.body.lastName,
    companyName=req.body.companyName,
    email=req.body.email;
});

I'd like to build a query up from these values, but if the field has no value, I obviously don't want to include it in the search (searching for "" would change the results)

I've tried a couple different things, like building a string to place in:

mongoose.model('customers').find({QUERY STRING WOULD GO HERE} ,function(err, data) {
    if (err) return console.error(err);
    console.log(data);
});

But that doesn't seem to work properly. I also tried "stacking" search queries like this:

if(firstName !="") {
    mongoose.model('customers').find({firstName: firstName})
}

and then executing the search like this:

mongoose.model('customers').exec(function(err, customer){
    console.log(customer);
});

But that causes 500 errors (and I'm not sure if there's any more info I can get from them).

Please help a Newbie dynamically build a mongoose search query :(

Answer 1

try creating query object, like:

//generate query object based on availability of value 
var query = {};
if( your_variable !== "" ) {
    query["some_key"] = your_variable;
}
if( your_second_variable !== "" ) {
    query["some_other_key"] = your_second_variable;
}
mongoose.model('customers').find(query, function(err, c) {
    //do something
});

Answer 2

For people using newer JavaScript (and especially on Node.js 7.6.0+ or Babel).

The best way I found for programmatically building queries (based on if clauses etc.) is using the Query and the alternative syntax.

let query = PersonModel().find();

if (isMale) {
    query.where('sex', 'male'); 
} else {
    query.where('sex', 'female');
}

query.where('alive', true);

// and then to run the query
const result = await query.exec();

Note the async/await usage here. It's working perfectly on Node.js 7.6.0+. If you don't want to use async/await you can just use Promises like so:

query.exec().then(result => {
    // result has your... results
});