angularjs modal模態框----創建可拖動的指令

//最近項目中需要將angular-ui-bootstrap中用到的彈出框，使之可拖動，由於源文件中沒有實現，需要自己實現指令，以下即為該指令，親測可以實現。
.directive('draggable', ['$document', function($document) {
                return function(scope, element, attr) {
                var startX = 0, startY = 0, x = 0, y = 0;
                element= angular.element(document.getElementsByClassName("modal-dialog")); 
                element.css({
                    position: 'relative',
                    cursor: 'move'
                });

                element.on('mousedown', function(event) {
                    // Prevent default dragging of selected content
                    event.preventDefault();
                    startX = event.pageX - x;
                    startY = event.pageY - y;
                    $document.on('mousemove', mousemove);
                    $document.on('mouseup', mouseup);
                });

                function mousemove(event) {
                    y = event.pageY - startY;
                    x = event.pageX - startX;
                    element.css({
                    top: y + 'px',
                    left:  x + 'px'
                    });
                }

                function mouseup() {
                    $document.off('mousemove', mousemove);
                    $document.off('mouseup', mouseup);
                }
                };
    }]);

 如圖：已不在屏幕中央，為拖動后的效果