Best way to take out keys with invalid (NaN, blank, etc) values from an object?

Question

I've got a short search form that a user fills out. There will be multiple search queries that will go into MongoDB:

The form creates a variable called searchParams that may look like this:

var searchParams = {
  city: "Springfield",
  bedrooms: 3,
  bathrooms: 2
};

I then have a function that takes the searchParams as an argument and queries Mongo using it:

var searchListings = function(searchParams){
  return db.MyListings.find(searchParams).fetch();
}

db.MyListings.find( {city: "Springfield", bedrooms: 3, bathrooms: 2} ).fetch();

This is all well and good for a complete searchParams object, but if the user doesn't fill out parts of the form and the object turns out to be this:

var searchParams = {
  city: "",
  bedrooms: NaN,
  bathrooms: 3
};

The query fails. It tries to literally search for a property with a city of "" and a bedroom of NaN.

What I want the query to be in the case of this object is just:

  db.MyListings.find( {bathrooms: 3} ).fetch();

I can go through each key one by one and check for NaN conditions and "" conditions and somehow remove the key from the searchParams object (I guess I'm like sterilizing the object?) but I was wondering if there was a more intelligent way to go about taking out the keys with invalid values?

I've got underscore installed.

UPDATE: This project is currently using Meteor 0.9.1. Meteor uses Underscore 1.0.0, which is why the below did not work:

The following doesn't seem to be working:

searchParams = {
  bathrooms: 3,
  bedrooms: NaN,
  city: "",
  exteriorSize: NaN,
  interiorSize: NaN,
  price: 0
};

console.log(searchParams);

newSearchParams = _.omit(searchParams, function(val) { 
  return !val;
});

console.log(newSearchParams); // exactly the same as searchParams

And if I do this:

searchParams = {
  bathrooms: 3,
  bedrooms: NaN,
  city: "",
  exteriorSize: NaN,
  interiorSize: NaN,
  price: 0
};

console.log(searchParams);

newSearchParams = _.pick(searchParams, function(val) { 
  return !!val;
});

console.log(newSearchParams); // blank object

Answer 1

With underscore 1.7.0+, you can easily filter the query object with _.pick():

searchParams = _.pick(searchParams, function(val) { 
  return !!val;
});

... that'll create an object with only those properties that were assigned truthy values.

You can do the same thing, but in a slightly different way, with _.omit():

searchParams = _.omit(searchParams, function(val) { 
  return !val;
});

In this case, all the properties with falsy values will be dropped.

---

For the completeness sake, here's a vanilla JS way:

var filteredSearchParams = {};
for (var prop in searchParams) {
  if (searchParams.hasOwnProperty(prop) && !!searchParams[prop]) {
    filteredSearchParams[prop] = searchParams[prop];
  }
}