var scrolltotop = { setting: { startline: 100, scrollto: 0, scrollduration: 500, fadeduration: [500, 100] }, controlHTML: '<img src="images/alert/top.png" style="width:50px; height:50px" />', controlattrs: { offsetx: 5, offsety: 5 }, anchorkeyword: '#top', state: { isvisible: false, shouldvisible: false }, scrollup: function () {
    if (!this.cssfixedsupport)
        this.$control.css({ opacity: 0 })
    var dest = isNaN(this.setting.scrollto) ? this.setting.scrollto : parseInt(this.setting.scrollto)
    if (typeof dest == "string" && jQuery('#' + dest).length == 1)
        dest = jQuery('#' + dest).offset().top
    else
        dest = 0
    this.$body.animate({ scrollTop: dest }, this.setting.scrollduration);
}, keepfixed: function () {
    var $window = jQuery(window)
    var controlx = $window.scrollLeft() + $window.width() - this.$control.width() - this.controlattrs.offsetx
    var controly = $window.scrollTop() + $window.height() - this.$control.height() - this.controlattrs.offsety
    this.$control.css({ left: controlx + 'px', top: controly + 'px' })
}, togglecontrol: function () {
    var scrolltop = jQuery(window).scrollTop()
    if (!this.cssfixedsupport)
        this.keepfixed()
    this.state.shouldvisible = (scrolltop >= this.setting.startline) ? true : false
    if (this.state.shouldvisible && !this.state.isvisible) {
        this.$control.stop().animate({ opacity: 1 }, this.setting.fadeduration[0])
        this.state.isvisible = true
    }
    else if (this.state.shouldvisible == false && this.state.isvisible) {
        this.$control.stop().animate({ opacity: 0 }, this.setting.fadeduration[1])
        this.state.isvisible = false
    } 
}, init: function () {
    jQuery(document).ready(function ($) {
        var mainobj = scrolltotop
        var iebrws = document.all
        mainobj.cssfixedsupport = !iebrws || iebrws && document.compatMode == "CSS1Compat" && window.XMLHttpRequest
        mainobj.$body = (window.opera) ? (document.compatMode == "CSS1Compat" ? $('html') : $('body')) : $('html,body')
        mainobj.$control = $('<div id="topcontrol">' + mainobj.controlHTML + '</div>').css({ position: mainobj.cssfixedsupport ? 'fixed' : 'absolute', bottom: mainobj.controlattrs.offsety, right: mainobj.controlattrs.offsetx, opacity: 0, cursor: 'pointer' }).attr({ title: 'Về đầu trang.' }).click(function () { mainobj.scrollup(); return false }).appendTo('body')
        if (document.all && !window.XMLHttpRequest && mainobj.$control.text() != '')
            mainobj.$control.css({ width: mainobj.$control.width() })
        mainobj.togglecontrol()
        $('a[href="' + mainobj.anchorkeyword + '"]').click(function () {
            mainobj.scrollup()
            return false
        })
        $(window).bind('scroll resize', function (e) { mainobj.togglecontrol() })
    })
} 
}
scrolltotop.init()