JavaScript实现鼠标拖动元素实例代码

$target.bind('mousedown', fn);

$(document)
.bind('mousemove', fn)
.bind('mouseup', fn);

// 阻止区域文字被选中 for chrome firefox ie9
e.preventDefault();
// for firefox ie9 || less than ie9
window.getSelection ? window.getSelection().removeAllRanges() : document.selection.empty();

e.preventDefault();

// x,y代表拖动元素将要设置的left,top值，limitObj为拖动区域范围对象，测试时就发现问题，
// 在拖动过程中，拖动对象有时不能直接靠近边界

if ( x >= limitObj._left && x <= limitObj._right ) {
    $target.css({ left: x + 'px' });
}
if ( y >= limitObj._top && y <= limitObj._bottom ) {
    $target.css({ top: y + 'px' });
}

if (x     x = limitObj._left;
}
if (x > limitObj._right) {
    x = limitObj._right;
}
if (y     y = limitObj._top;
}
if (y > limitObj._bottom) {
    y = limitObj._bottom;
}
$target.css({ left: x + 'px', top: y + 'px' });

$target.css({
    left: Math.max( Math.min(x, limitObj._right),  limitObj._left) + 'px',
    top: Math.max( Math.min(y, limitObj._bottom),  limitObj._top) + 'px'
});

$.fn.extend({
    /**
     *   Autor: 博客园华子yjh 2014/02/21
     */
    drag: function(options) {
        var dragStart, dragMove, dragEnd,
            $boundaryElem, limitObj;

        function _initOptions() {
            var noop = function(){}, defaultOptions;

            defaultOptiOns= { // 默认配置项
                boundaryElem: 'body' // 边界容器
            };
            optiOns= $.extend( defaultOptions, options || {} );
            $boundaryElem = $(options.boundaryElem);

            dragStart = options.dragStart || noop,
            dragMove = options.dragMove || noop,
            dragEnd = options.dragEnd || noop;
        }

        function _drag(e) {
            var clientX, clientY, offsetLeft, offsetTop,
                $target = $(this), self = this;

            limitObj = {
                _left: 0,
                _top: 0,
                _right: ($boundaryElem.innerWidth() || $(window).width()) - $target.outerWidth(),
                _bottom: ($boundaryElem.innerHeight() || $(window).height()) - $target.outerHeight()
            };

            // 记录鼠标按下时的位置及拖动元素的相对位置
            clientX = e.clientX;
            clientY = e.clientY;
            offsetLeft = this.offsetLeft;
            offsetTop = this.offsetTop;

            dragStart.apply(this, arguments);
            $(document).bind('mousemove', moveHandle)
                        .bind('mouseup', upHandle);

            // 鼠标移动事件处理
            function moveHandle(e) {
                var x = e.clientX - clientX + offsetLeft;
                var y = e.clientY - clientY + offsetTop;

                $target.css({
                    left: Math.max( Math.min(x, limitObj._right),  limitObj._left) + 'px',
                    top: Math.max( Math.min(y, limitObj._bottom),  limitObj._top) + 'px'
                });

                dragMove.apply(self, arguments);
                // 阻止浏览器默认行为(鼠标在拖动图片一小段距离，会出现一个禁止的小提示，即：图片不能再拖动)
                e.preventDefault();
            }

            // 鼠标弹起事件处理
            function upHandle(e) {
                $(document).unbind('mousemove', moveHandle);
                dragEnd.apply(self, arguments);
            }
        }

        _initOptions(); // 初始化配置对象

        $(this)
        .css({ position: 'absolute' })
        .each(function(){
            $(this).bind('mousedown', function(e){
                _drag.apply(this, [e]);
                // 阻止区域文字被选中 for chrome firefox ie9
                e.preventDefault();
                // for firefox ie9 || less than ie9
                window.getSelection ? window.getSelection().removeAllRanges() : document.selection.empty();
            });
        });
        return this;
    }
});

// 调用实例
(function(){
    $('.drag-elem').drag({
        boundaryElem: '#boundary',
        dragStart: function(){
            $(this).html('准备拖动').css({ zIndex: 2 }).siblings().css({ zIndex: 1 });
        },
        dragMove: function(){
            var pos = $(this).position();
            $(this).html('拖动中(' +  pos.left + ',' + pos.top + ')' );
        },
        dragEnd : function(){
            $(this).html('拖动结束');           
        }
    });
}());