gistfile1.txt

var sanitizer = function(valids, unsettable) {
	var compile = function(valid, value) {
		var fn = Object.prototype.toString.call(value) === '[object RegExp]' ? 
					function(query, set, unset) {
						if (query[valid] && value.test(query[valid])) {
							set[valid] = query[valid];
						}
					} : 
					function(query, set, unset) {
						if (valid in query) {
							set[valid] = query[valid];							
						}
					};

		if (unsettable) {
			return function(query, set, unset) {
				if (query[valid] in {'undefined':1, 'null':1}) {
					unset[valid] = 1;
				} else {
					fn(query, set, unset);
				}
			};
		}
		return fn;
	}
	
	var fns = [];

	for (var i in valids) {
		fns.push(compile(i, valids[i]));
	}
	
	return function(query) {
		var set = {};
		var unset = {};
		
		fns.forEach(function(fn) {
			fn(query, set, unset);
		});
		
		return {$set:set, $unset:unset};
	};
};