An underscore.js mixin for picking nested properties by keeping the nested structure.

nestedPick.js

_.mixin({
	nestedPick: function (obj, wantedKeys) {
		var resultObj = {};
		_.forEach(wantedKeys, function (key) {
			// Parsing nested keys. Making it so that a[b] equals a.b
			var nestedKeys = key.replace(/\[(["']?)([^\1]+?)\1?\]/g, '.$2').replace(/^\./, '').split('.')
			  , finalVal = {}
			  , dummy = {}
			  , recVal = obj[nestedKeys[0]]
			  , j = 1
			  , nestedVal;

			if(nestedKeys.length == 1) {
				resultObj[key] = obj[key];
				return;
			}
			// Receive nested value
			while(_.isUndefined(recVal) && j < nestedKeys.length) {
				nestedVal = recVal;
				recVal = recVal[nestedKeys[j++]];
			}
			// Continue looping value is not present
			if(_.isUndefined(recVal))
				return;
			else {
				// Build nested value
				nestedVal = recVal;
				finalVal[_.last(nestedKeys)] = nestedVal;
				for(var i = nestedKeys.length-2; i > 0; i--) {
					dummy[nestedKeys[i]] = finalVal;
					finalVal = dummy;
				}
			}
			// Add value to the final object
			resultObj[nestedKeys[0]] = finalVal;
		});
		return resultObj;
	}
});

nestedPick_example.js

// Example Object
var user = {
	accounts: {
		facebook: {
			email: 'foo@example.com',
			username: 'foobar',
			accessToken: 'secretSauce'
		},
		twitter: {}
	},
	password: 'secretSauce',
	totalLikes: 1234
}

// Example Usage
var filteredUser = _.nestedPick(user, ['accounts.facebook.email', 'totalLikes']);