angularjs DIV滚动条置底

//DIV滚动条置底
$scope.scrollWindow=function(){
    var _el = document.getElementById('chat_history');
    //_el.scrollTop = _el.scrollHeight;
    _el.scrollTop = _el.scrollHeight;
};


//----使用方法
 setTimeout(function(){
    $scope.scrollWindow();
},500);