这是很简单的js拖拽方法

var funDrag = function(element, callback) {
    callback = callback || function() {};
    var params = {
        left: 0,
        top: 0,
        currentX: 0,
        currentY: 0,
        flag: false
    };
    //获取相关CSS属性
    var getCss = function(o,key){
        return o.currentStyle? o.currentStyle[key] : document.defaultView.getComputedStyle(o,false)[key];     
    };
    
    //拖拽的实现
    if(getCss(element, "left") !== "auto"){
        params.left = getCss(element, "left");
    }
    if(getCss(element, "top") !== "auto"){
        params.top = getCss(element, "top");
    }
    //o是移动对象
    element.onmousedown = function(event){
        params.flag = true;
        event = event || window.event;
        params.currentX = event.clientX;
        params.currentY = event.clientY;
    };
    document.onmouseup = function(){
        params.flag = false;    
        if(getCss(element, "left") !== "auto"){
            params.left = getCss(element, "left");
        }
        if(getCss(element, "top") !== "auto"){
            params.top = getCss(element, "top");
        }
        callback();
    };
    document.onmousemove = function(event){
        event = event || window.event;
        if(params.flag){
            var nowX = event.clientX, nowY = event.clientY;
            var disX = nowX - params.currentX, disY = nowY - params.currentY;
            element.style.left = parseInt(params.left) + disX + "px";
            element.style.top = parseInt(params.top) + disY + "px";
        }
    }    
};