jquery 返回顶端组件

自己写了一个基于jquery的返回页面顶端的组件。

(function($) {
var g;
$.backtop = function(options) {
extend($.backtop.config, options);
this.config = $.backtop.config;
this.init();
g = this;
};
$.backtop.config = {
title : null,// 返回顶端文字说明
df_color : "#77AA55"// 组件默认颜色
};
$.backtop.prototype = {
config : null,
backtop : null,// 当前创建返回顶端对象
init : function() {
this._scrool();
},
_scrool : function() {
window.onscroll = function() {
g._create_ob($(window).scrollTop());
};
},
_create_ob : function(top) {
if(top==0){
$("#back_top").remove();
return;
}
$("#back_top").remove();
this.backtop = $("<div class='mouseover'><img src='ui/main/gotop.gif'></img></div>");
$(this.backtop).bind("click",function(){
g._moveTo();
});
$(this.backtop).bind("mouseover",function(){
$(g.backtop).removeClass();
$(g.backtop).addClass("mouse");
});
$(this.backtop).bind("mouseout",function(){
$(g.backtop).removeClass();
$(g.backtop).addClass("mouseover");
});
$(this.backtop).attr("id","back_top");
/*$(this.backtop).css("backgroundColor", this.config.df_color);*/
$(this.backtop).css("zIndex", 1000);
$(this.backtop).css("position", "absolute");
$(this.backtop).css("cursor","pointer");
$(this.backtop).width(30);
$(this.backtop).height(30);
$(this.backtop).css("left",$("body").attr("clientWidth")-50);
$(this.backtop).css("top", top+300);
$("body").append(this.backtop);
},// 创建返回顶端jquery对象
_moveTo:function(){
$("#back_top").remove();
window.scroll(0,0);
}
};
})(jQuery);
var extend = function($cf, options) {
for ( var a in options) {
$cf[a] = options[a];
}
};