Auto-expanding Textarea Directive

myApp.directive("autoGrow", function(){
    return function(scope, element, attr){
        var update = function(){
            element.css("height", "auto");
            element.css("height", element[0].scrollHeight + "px");
        };
        scope.$watch(attr.ngModel, function(){
            update();
        });
        attr.$set("ngTrim", "false");
    };
});