Mongoose complex queries with optional parameters?

Question

I'm relatively new to Mongo & mongoose, and I've hit a problem.

I have a reasonably (for me anyway) complex query, that will allow the user to search for all entered terms.

so if the query is something like so:

var query = { '$and' : [
    { "foo1" : "bar1" },
    { '$and' : [ "foor2" : { $ne : null } }, { "foo2" : "bar2" } ] },
    { "foo3" : "bar3" }
]};

Doc.find(query);

but the user can enter any number of combinations for the parameters, i.e. I could search for all items that match foo1 & foo2, or just all items that match foo2, or just foo3, etc.

Is there a way to tell the query to only look for a parameter if it isn't empty, or is there a way to build searches like this programmatically? I have seen other options, for adding parameters like this, but they only seem to add in the standard

{ foo : 'bar' }

format, and for some reason they always seem to get added to query whether they meet the conditions of the if statement or not.

Thanks.

Talha Awan · Accepted Answer · 2017-07-25 18:02:36Z

3

Firstly, you don't need $and operator for what you want. Comma separation is implicit and.

Your example query should simply be:

var query = {
    "foo1": "bar1",
    //"foo2": { $ne: null}, is unnecessary as "foo2" is being searched for "bar2" already, so it won't be null
    "foo2": "bar2",
    "foo3": "bar3"
};

To build this query dynamically, you can check the parameters (say req.body) one by one and add them to query object with bracket notation:

var query = {};

if (req.body.foo1) {
    query["foo1"] = req.body.foo1
}

if (req.body.foo2) {
    query["foo2"] = req.body.foo2;
}

if (req.body.foo3) {
    query["foo3"] = req.body.foo3;
}

Or, you can loop through the parameters and build the same query object if you are sure what they contain:

var query = {};

for(var key in req.body){ 
  query[key] = req.body[key];
}

answered Jul 25, 2017 at 18:02

Talha Awan

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1 Comment

user3075259 Over a year ago

Cool thanks for that, I managed to figure out how to do it like this, but nice to know I came to the right solution. I think I'd made life a bit harder for myself by making a query that looked more complicated than it needed to be. Rookie mistake :)

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