Neater way to filter Object containing other Objects by value

I've got a JavaScript object that looks like this:

var options = { 
    'user1' : { 'house1' : ["lat1", "lng1"] },
    'user2' : { 'house2' : ["lat2", "lng2"] },
    'user3' : { 'house1' : ["lat3", "lng3"] }
};

Say I want to look up a开发者_运维技巧ll the users associated with house1, and return an array of their usernames and their positions.

What's the clearest and most efficient way to do this?

Currently I've written a rather unwieldy custom lookup, as follows:

function returnByValues(options, housenum):
    var results = [];
    for (var username in options) { 
        var properties = options[username];
        for (var housekey in properties) { 
            if (housekey === housenum) { 
                var result = {};
                result[username] = properties;
                results.push(result);
            }
        }
    } 
    return results;

Is there a neater way? It's not exactly readable code!

I don't think you need the middle loop, assuming each user is only associated with one house as per your example. So:

function returnByValues(options, housenum):
    var results = [];
    for (var username in options) { 
        var properties = options[username];
        if (housenum in properties) {
            var result = {};
            result[username] = properties;
            results.push(result);
        }
    } 
    return results;
}

You don't often see the if (housenum in properties) syntax, but it's a more elegant equivalent of if (properties[housenum] != undefined).

By the way, your code:

result[username] = properties;

gives result == {"user1" : { 'house1' : [lat, lng] } } - is that your intention? Because your description of what you want was "an array of their usernames and their positions" which I would take to be this:

result[username] = properties[housenum];

giving result == {"user1" : [lat, lng] }

I guess you search for sth like this: filteredArray = array.filter( ... return a.xyz == b.xyz )

If so, take a look at this: http://www.tutorialspoint.com/javascript/array_filter.htm

function returnByValues(options, housenum){
    var results = [];
    for (var username in options)
        if(housenum in options[username])
        results.push(function(){ 
            var obj={}; 
            obj[username] = options[username]; 
            return obj;
        });
    return results;
}

If you wanted to use linq.js, you could do things along the lines of

function returnByValues(users, house) {
  return Enumerable.From(users).Where("'" + house + "' in $.Value")
  .ToObject("$.Key", "$.Value");
}

where this

var searchResult = returnByValues(options, "house1");

/* yields:
{
    "user1": {
        "house1": ["lat1", "lng1"]
    },
    "user3": {
        "house1": ["lat3", "lng3"]
    }
}
*/

Look at a working example on jsFiddle.