Native JavaScript function that performs deep-copy/merge capabilities on n number of arguments. Returns merged object. Adapted from: http://stackoverflow.com/questions/171251/how-can-i-merge-properties-of-two-javascript-objects-dynamically

merge-javacript-objects

var obj1 = {
	"foo": {
		"dog": "000"
	},
	"bar": {
		"bear": "111"
	},
	"tee": {
		"elephant": "555"
	}
};

var obj2 = {
	"foo": {
		"cat": "222"
	},
	"bar": {
		"monkey": "333"
	},
	"moo": {
		"snake": "444"
	}
};

/**
 * Function takes any number of arguments. It can be used to merge objects and makes deep copies of
 * values. However, first argument is given by reference.
 *
 * @returns {*}
 */
function merge() {

	/**
	 * Determines if an object is valid.
	 *
	 * @param {Object} obj The object being checked for validity.
	 * @returns {boolean} Boolean value indicating if the object is valid.
	 * @private
	 */
	var _isValidObject = function(obj) {
		return ( (typeof obj !== 'object') || (obj === null) );
	}

	/**
	 * Inner function that merges two object and their properties.
	 *
	 * @param {Object} dst The destination object that contains the merged properties.
	 * @param {Object} src The source object that's being merged into the destination object.
	 * @returns {*} The final, merged object; aka the destination object.
	 * @private
	 */
	var _mergeObjects = function(dst, src) {
		if(_isValidObject(src)) {
			return dst;
		}

		for(var p in src) {
			if(!src.hasOwnProperty(p)) {
				continue;
			}
			if(src[p] === undefined) {
				continue;
			}
			if(_isValidObject(src[p])) {
				dst[p] = src[p];
			} else if(_isValidObject(dst[p])) {
				dst[p] = _mergeObjects(src[p].constructor === Array ? [] : {}, src[p]);
			} else {
				_mergeObjects(dst[p], src[p]);
			}
		}
		return dst;
	};

	// Loop through arguments and merge them into the first argument.
	var out = arguments[0];
	if(_isValidObject(out)) {
		return out;
	}
	for(var i = 1, il = arguments.length; i < il; i++) {
		_mergeObjects(out, arguments[i]);
	}
	return out;
}

var mergedObject = merge(obj1, obj2);

/*
// Result
mergedObject = {
	bar: {
		bear: "111",
		monkey: "333"
	},
	foo: {
		cat: "222",
		dog: "000"
	},
	moo: {
		snake: "444"
	},
	tee: {
		elephant: "555"
	}
}
*/

Some clarity on the for loop:

for(var p in src) 
{   
    if( src.hasOwnProperty(p) ) 
    {
        var sVal    = src[ p ],
            dVal    = dst[ p ];

        if( sVal !== undefined) 
        {
            if( _isValidObject( sVal )) 
            {
                dst[p] = sVal;
            }
            else if( _isValidObject( dVal )) 
            {
                dst[p] = _mergeObjects ( 
                            sVal.constructor === Array ? [] : {}, 
                            sVal 
                        );

            } else {
                _mergeObjects( dVal, sVal );
            }
        }
    }
}