Share code JavaScript nút Go TOP - Bottom ở góc dưới, bên phải trang Wap

var vtlai_dy=350;

var vtlai_dtime=4;



function vtlai_gettop()

{

try{

if(window.pageYOffset!=undefined)

return window.pageYOffset;

return window.document.body.scrollTop;

}catch(err)

{

try{

return window.document.body.scrollTop;

}catch(err2)

{

return 0;

}

}



}

function vtlai_croll_top()

{



var vtlai_body_obj=window.document.body;

var vtlai_cur_stop=vtlai_gettop();

window.scrollBy (0,-vtlai_dy);

var vtlai_new_stop=vtlai_gettop();

if(vtlai_cur_stop>vtlai_new_stop)

setTimeout("vtlai_croll_top()",vtlai_dtime);

else

document.getElementById("vtlai_scroll_down_img").style.display="block";

return false;

}



function vtlai_croll_down()

{

var vtlai_body_obj=window.document.body;

var vtlai_cur_stop=vtlai_gettop();

window.scrollBy (0,vtlai_dy);

var vtlai_new_stop=vtlai_gettop();

if(vtlai_cur_stop<vtlai_new_stop)

setTimeout("vtlai_croll_down()",vtlai_dtime);

else

document.getElementById("vtlai_scroll_down_img").style.display="none";

return false;

}



function vtlai_display_scroll_btn()

{

var vtlai_body=window.document.body;

var vtlai_height=vtlai_body.scrollHeight;

var vtlai_top=vtlai_gettop();

//document.getElementById("scroll").innerHTML=vtlai_top+"/"+vtlai_height;

if(vtlai_top==0)

document.getElementById("vtlai_scroll_up_img").style.display="none";

else

document.getElementById("vtlai_scroll_up_img").style.display="block";

/*

if(vtlai_top>=vtlai_height-vtlai_body.clientHeight)

document.getElementById("vtlai_scroll_down_img").style.display="none";

else

document.getElementById("vtlai_scroll_down_img").style.display="block";

*/

}

setInterval("vtlai_display_scroll_btn()",100);

document.write('<div style="position: fixed; filter: alpha(opacity=40); opacity:0.4; width: 40px; right: 5px; bottom: 35px; -moz-transition: 0.5s ease-in; -webkit-transition: 0.5s ease-in; -o-transition: 0.5s ease-in; transition: 0.5s ease-in;" onmouseover="this.style.opacity=1;this.filters.alpha.opacity=100"onmouseout="this.style.opacity=0.4;this.filters.alpha.opacity=40"><a href="#" onclick="return vtlai_croll_top()"><img border="0" id="vtlai_scroll_up_img" src="http://i41.servimg.com/u/f41/16/91/68/14/top10.png"></a> <br /><br /> <a href="#" onclick="return vtlai_croll_down()"><img border="0" id="vtlai_scroll_down_img" src="http://i41.servimg.com/u/f41/16/91/68/14/buttom10.png"></a></div></div>');

<script language="javascript" type="text/javascript" src="link tới file .js"></script>