Filtering a JSON object through a template

Question

Filtering a JSON object through a template

I need to filter JSON objects' properties and values based on a dynamic template (for security reasons). It is like viewing the JSON objects through a mask that is known only at run time.

Say I have this JSON object:

{ "id": "1",
  "foo": [ "1", "2", "3" ],
  "bar": [ "a", "b", "c"],
  "fuzz": [ "y", "x" ]
}

And this template:

{ "id": "",
  "fuzz": [ "y", "z"],
  "foo": ""
}

Now I want to have the following result (applying the template onto the object):

{ "id": "1",
  "fuzz": [ "y" ],
  "foo": [ "1", "2", "3" ]
}

What are the best solutions to filter

Only the properties (leaving values untouched)?
The properties and the values (like in the example above)?

Notes:

The ordering of properties and values may be different between the template and the objects
My environment is NodeJS + BackboneJS
A have a lot of objects to filter, so performance matters

javascript
json
node.js
backbone.js

Answer 1

Based on the WiredPrairie's suggestion, I rewrote _.pick() and _.intersection() into the following method that does the trick:

// Loosely based on Underscore.js _.pick() method
function project(obj, tmp) {
    var copy = {};
    var keys = _.keys(tmp);
    _.each(keys, function(key) {
        if (key in obj) {
            var vals = tmp[key];
            if (Array.isArray(vals)) {
                var copy_vals = [];
                // Next lines could be replaced by:
                // cvals = _.intersection(vals, obj[key]);
                _.each(vals, function(val) {
                    if ($.inArray(val, obj[key])!=-1) {
                        copy_vals.push(val);
                    };
                });
                copy[key] = copy_vals;
            } else {
                copy[key] = obj[key];
            };
        };
    });
    return copy;
}

Answer 2

I'm not sure but you could try read this one jQuery.extend