JS 禁用背景頁面滾動

var s_top=0;
    // 禁止滾動
    function bodyScroll(event){  
        event.preventDefault();  
    }

    //禁止背景頁面滾動
    function unScroll(){
        s_top = $(window).scrollTop();
        document.body.addEventListener('touchmove',bodyScroll,false);  
        $('body').css({'position':'fixed',"width":"100%"});
    }

    // 恢復背景頁面滾動
    function scroll(){
        document.body.removeEventListener('touchmove',bodyScroll,false);   
        $("body").css({"position":"initial","height":"auto"});
        $(window).scrollTop(s_top);
    }