function beginMove()

in _dist/alertify/alertify.js [1615:1682]
55 lines of code
14 McCabe index (conditional complexity)

        function beginMove(event, instance) {
            if (resizable === null && !instance.isMaximized() && instance.get('movable')) {
                var eventSrc, left=0, top=0;
                if (event.type === 'touchstart') {
                    event.preventDefault();
                    eventSrc = event.targetTouches[0];
                    xProp = 'clientX';
                    yProp = 'clientY';
                } else if (event.button === 0) {
                    eventSrc = event;
                }

                if (eventSrc) {

                    var element = instance.elements.dialog;
                    addClass(element, classes.capture);

                    if (element.style.left) {
                        left = parseInt(element.style.left, 10);
                    }

                    if (element.style.top) {
                        top = parseInt(element.style.top, 10);
                    }
                    
                    offsetX = eventSrc[xProp] - left;
                    offsetY = eventSrc[yProp] - top;

                    if(instance.isModal()){
                        offsetY += instance.elements.modal.scrollTop;
                    }else if(instance.isPinned()){
                        offsetY -= document.body.scrollTop;
                    }
                    
                    if(instance.get('moveBounded')){
                        var current = element,
                            offsetLeft = -left,
                            offsetTop = -top;
                        
                        //calc offset
                        do {
                            offsetLeft += current.offsetLeft;
                            offsetTop += current.offsetTop;
                        } while (current = current.offsetParent);
                        
                        bounds = {
                            maxLeft : offsetLeft,
                            minLeft : -offsetLeft,
                            maxTop  : document.documentElement.clientHeight - element.clientHeight - offsetTop,
                            minTop  : -offsetTop
                        };
                        moveDelegate = moveElementBounded;
                    }else{
                        bounds = null;
                        moveDelegate = moveElement;
                    }
                    
                    // allow custom `onmove` method
                    dispatchEvent('onmove', instance);

                    refreshTop = !instance.isModal() && instance.isPinned();
                    movable = instance;
                    moveDelegate(eventSrc, element);
                    addClass(document.body, classes.noSelection);
                    return false;
                }
            }
        }