JS CSS drop-down menu background problem_html/css_WEB-ITnose

select scroll bar

The following code changes the style of the drop-down menu and can be used normally. However, there is a problem now that there is a lot of content in the drop-down menu. I think there will be a scroll bar automatically at a certain height. Could anyone help me please, thank you very much.

<script language="JavaScript" type="text/javascript">var selects = document.getElementsByTagName('select');var isIE = (document.all && window.ActiveXObject && !window.opera) ? true : false;function $(id) {	return document.getElementById(id);}function stopBubbling (ev) {		ev.stopPropagation();}function rSelects() {	for (i=0;i<selects.length;i++){		selects[i].style.display = 'none';		select_tag = document.createElement('div');			select_tag.id = 'select_' + selects[i].name;			select_tag.className = 'select_box';		selects[i].parentNode.insertBefore(select_tag,selects[i]);		select_info = document.createElement('div');				select_info.id = 'select_info_' + selects[i].name;			select_info.className='tag_select';			select_info.style.cursor='pointer';		select_tag.appendChild(select_info);		select_ul = document.createElement('ul');				select_ul.id = 'options_' + selects[i].name;			select_ul.className = 'tag_options';			select_ul.style.position='absolute';			select_ul.style.display='none';			select_ul.style.zIndex='999';		select_tag.appendChild(select_ul);		rOptions(i,selects[i].name);				mouseSelects(selects[i].name);		if (isIE){			selects[i].onclick = new Function("clickLabels3('"+selects[i].name+"');window.event.cancelBubble = true;");		}		else if(!isIE){			selects[i].onclick = new Function("clickLabels3('"+selects[i].name+"')");			selects[i].addEventListener("click", stopBubbling, false);		}			}}function rOptions(i, name) {	var options = selects[i].getElementsByTagName('option');	var options_ul = 'options_' + name;	for (n=0;n<selects[i].options.length;n++){			option_li = document.createElement('li');			option_li.style.cursor='pointer';			option_li.className='open';		$(options_ul).appendChild(option_li);		option_text = document.createTextNode(selects[i].options[n].text);		option_li.appendChild(option_text);		option_selected = selects[i].options[n].selected;		if(option_selected){			option_li.className='open_selected';			option_li.id='selected_' + name;			$('select_info_' + name).appendChild(document.createTextNode(option_li.innerHTML));		}				option_li.onmouseover = function(){	this.className='open_hover';}		option_li.onmouseout = function(){			if(this.id=='selected_' + name){				this.className='open_selected';			}			else {				this.className='open';			}		} 			option_li.onclick = new Function("clickOptions("+i+","+n+",'"+selects[i].name+"')");	}}function mouseSelects(name){	var sincn = 'select_info_' + name;	$(sincn).onmouseover = function(){ if(this.className=='tag_select') this.className='tag_select_hover'; }	$(sincn).onmouseout = function(){ if(this.className=='tag_select_hover') this.className='tag_select'; }	if (isIE){		$(sincn).onclick = new Function("clickSelects('"+name+"');window.event.cancelBubble = true;");	}	else if(!isIE){		$(sincn).onclick = new Function("clickSelects('"+name+"');");		$('select_info_' +name).addEventListener("click", stopBubbling, false);	}}function clickSelects(name){	var sincn = 'select_info_' + name;	var sinul = 'options_' + name;		for (i=0;i<selects.length;i++){			if(selects[i].name == name){							if( $(sincn).className =='tag_select_hover'){				$(sincn).className ='tag_select_open';				$(sinul).style.display = '';			}			else if( $(sincn).className =='tag_select_open'){				$(sincn).className = 'tag_select_hover';				$(sinul).style.display = 'none';			}		}		else{			$('select_info_' + selects[i].name).className = 'tag_select';			$('options_' + selects[i].name).style.display = 'none';		}	}}function clickOptions(i, n, name){			var li = $('options_' + name).getElementsByTagName('li');	$('selected_' + name).className='open';	$('selected_' + name).id='';	li[n].id='selected_' + name;	li[n].className='open_hover';	$('select_' + name).removeChild($('select_info_' + name));	select_info = document.createElement('div');		select_info.id = 'select_info_' + name;		select_info.className='tag_select';		select_info.style.cursor='pointer';	$('options_' + name).parentNode.insertBefore(select_info,$('options_' + name));	mouseSelects(name);	$('select_info_' + name).appendChild(document.createTextNode(li[n].innerHTML));	$( 'options_' + name ).style.display = 'none' ;	$( 'select_info_' + name ).className = 'tag_select';	selects[i].options[n].selected = 'selected';}window.onload = function(e) {	bodyclick = document.getElementsByTagName('body').item(0);	rSelects();	bodyclick.onclick = function(){		for (i=0;i<selects.length;i++){				$('select_info_' + selects[i].name).className = 'tag_select';			$('options_' + selects[i].name).style.display = 'none';		}	}}</script>

<style type="text/css">body{margin:0px; padding:0px; font-size:12px; color:#FFFFFB; background:#3d4045;   }div,ul,li{margin:0; padding:0;}#macstyle1 .select_box{height:22px;  width:271px;}#macstyle1 div.tag_select{display:block;color:#fff; text-align:left; padding-left:10px;width:271px;height:22px;background:url(http://img.bbs.csdn.net/upload/201307/03/1372819568_91197.gif) no-repeat;line-height:22px;}#macstyle1 div.tag_select_hover{display:block;color:#fff;text-align:left; padding-left:10px;width:271px;height:22px;background:url(http://img.bbs.csdn.net/upload/201307/03/1372819568_91197.gif) no-repeat;line-height:22px;}#macstyle1 div.tag_select_open{display:block;color:#fff;text-align:left; padding-left:10px;width:271px;height:22px;background:url(http://img.bbs.csdn.net/upload/201307/03/1372819568_91197.gif) no-repeat;line-height:22px;}#macstyle1 ul.tag_options{position:absolute;list-style:none;text-align:left;  }#macstyle1 ul.tag_options li{ background:#414348;text-align:left; padding-left:10px;width:241px;height:15px;line-height:15px;color:#fff;overflow:auto;}#macstyle1 ul.tag_options li.open_hover{color:#fff; background:#6c6f75; }#macstyle1 ul.tag_options li.open_selected{color:#fff; }</style>

<div id="macstyle1">            <select >              <option  value="GMT-12:00">GMT-12:00 日界线西</option>              <option  value="GMT-11:00">GMT-11:00 中途岛，萨摩亚群岛</option>              <option  value="GMT-10:00">GMT-10:00 夏威夷</option>              <option  value="GMT-9:00">GMT-9:00 阿拉斯加</option>              <option  value="GMT-8:00">GMT-8:00 太平洋时间(美国和加拿大)</option>              <option  value="GMT-7:00">GMT-7:00 山地时间(美国和加拿大)</option>              <option  value="GMT-6:00">GMT-6:00 中部时间(美国和加拿大)</option>              <option  value="GMT-5:00">GMT-5:00 东部时间(美国和加拿大)</option>              <option  value="GMT-4:30">GMT-4:30 加拉斯加</option>              <option  value="GMT-4:00">GMT-4:00 大西洋时间(加拿大)</option>              <option  value="GMT-3:30">GMT-3:30 纽芬兰</option>              <option  value="GMT-3:00">GMT-3:00 乔治郭、巴西利亚</option>              <option  value="GMT-2:00">GMT-2:00 中大西洋</option>              <option  value="GMT-1:00">GMT-1:00 佛得角群岛、亚速尔群岛</option>              <option  value="GMT-0:00">GMT-0:00 都柏林、爱丁堡、伦敦</option>              <option  value="GMT+1:00">GMT+1:00 阿姆斯特丹、柏林、罗马、巴黎</option>              <option  value="GMT+2:00">GMT+2:00 雅典、耶路撒冷、伊斯坦布尔</option>              <option  value="GMT+3:00">GMT+3:00 巴格达、科威特、莫斯科</option>              <option  value="GMT+3:30">GMT+3:30 德黑兰</option>              <option  value="GMT+4:00">GMT+4:00 高加索标准时间</option>              <option  value="GMT+4:30">GMT+4:30 喀布尔</option>              <option  value="GMT+5:00">GMT+5:00 伊斯兰堡、卡拉奇、塔什干</option>              <option  value="GMT+5:30">GMT+5:30 马德拉斯、孟买、新德里</option>              <option  value="GMT+5:45">GMT+5:45 加德满都</option>              <option  value="GMT+6:00">GMT+6:00 阿拉木图、新西伯利亚、达卡</option>              <option  value="GMT+6:30">GMT+6:30 仰光</option>              <option  value="GMT+7:00">GMT+7:00 曼谷、河内、雅加达</option>              <option  value="GMT+8:00" selected="selected">GMT+8:00 北京、乌鲁木齐、新加坡</option>              <option  value="GMT+9:00">GMT+9:00 汉城、东京、大阪、札幌</option>              <option  value="GMT+9:30" >GMT+9:30 阿德莱德、达尔文</option>              <option  value="GMT+10:00" >GMT+10:00 墨尔本、悉尼、堪培拉</option>              <option  value="GMT+11:00">GMT+11:00 马加丹、索罗门群岛</option>              <option  value="GMT+12:00">GMT+12:00 奥克兰、惠灵顿</option>              <option  value="GMT+13:00">GMT+13:00 努库阿洛法</option>            </select>          </div> 

Reply to discussion (solution)

The default overflow is visible. It will open automatically. Just give #macstyle1 ul.tag_options a suitable height and set overflow-y:auto;. For the sake of beauty, overflow-x can be set to hidden. After the scroll bar comes out, the width is a bit insufficient. It is recommended to add a little more.

<!doctype html><html><head><meta charset="utf-8" /><style type="text/css">body{margin:0px; padding:0px; font-size:12px; color:#FFFFFB; background:#3d4045;   }div,ul,li{margin:0; padding:0;}#macstyle1 .select_box{height:22px;  width:271px;}#macstyle1 div.tag_select{display:block;color:#fff; text-align:left; padding-left:10px;width:271px;height:22px;background:url(http://img.bbs.csdn.net/upload/201307/03/1372819568_91197.gif) no-repeat;line-height:22px;}#macstyle1 div.tag_select_hover{display:block;color:#fff;text-align:left; padding-left:10px;width:271px;height:22px;background:url(http://img.bbs.csdn.net/upload/201307/03/1372819568_91197.gif) no-repeat;line-height:22px;}#macstyle1 div.tag_select_open{display:block;color:#fff;text-align:left; padding-left:10px;width:271px;height:22px;background:url(http://img.bbs.csdn.net/upload/201307/03/1372819568_91197.gif) no-repeat;line-height:22px;}#macstyle1 ul.tag_options{position:absolute;list-style:none;text-align:left;height:300px;overflow-y:auto;overflow-x:hidden;}#macstyle1 ul.tag_options li{ background:#414348;text-align:left; padding-left:10px;width:241px;height:15px;line-height:15px;color:#fff;overflow:auto;}#macstyle1 ul.tag_options li.open_hover{color:#fff; background:#6c6f75; }#macstyle1 ul.tag_options li.open_selected{color:#fff; }</style><script language="JavaScript" type="text/javascript">var selects = document.getElementsByTagName('select'); var isIE = (document.all && window.ActiveXObject && !window.opera) ? true : false; function $(id) {    return document.getElementById(id);} function stopBubbling (ev) {        ev.stopPropagation();} function rSelects() {    for (i=0;i<selects.length;i++){        selects[i].style.display = 'none';        select_tag = document.createElement('div');            select_tag.id = 'select_' + selects[i].name;            select_tag.className = 'select_box';        selects[i].parentNode.insertBefore(select_tag,selects[i]);         select_info = document.createElement('div');                select_info.id = 'select_info_' + selects[i].name;            select_info.className='tag_select';            select_info.style.cursor='pointer';        select_tag.appendChild(select_info);         select_ul = document.createElement('ul');                select_ul.id = 'options_' + selects[i].name;            select_ul.className = 'tag_options';            select_ul.style.position='absolute';            select_ul.style.display='none';            select_ul.style.zIndex='999';        select_tag.appendChild(select_ul);         rOptions(i,selects[i].name);                 mouseSelects(selects[i].name);         if (isIE){            selects[i].onclick = new Function("clickLabels3('"+selects[i].name+"');window.event.cancelBubble = true;");        }        else if(!isIE){            selects[i].onclick = new Function("clickLabels3('"+selects[i].name+"')");            selects[i].addEventListener("click", stopBubbling, false);        }            }}  function rOptions(i, name) {    var options = selects[i].getElementsByTagName('option');    var options_ul = 'options_' + name;    for (n=0;n<selects[i].options.length;n++){            option_li = document.createElement('li');            option_li.style.cursor='pointer';            option_li.className='open';        $(options_ul).appendChild(option_li);         option_text = document.createTextNode(selects[i].options[n].text);        option_li.appendChild(option_text);         option_selected = selects[i].options[n].selected;         if(option_selected){            option_li.className='open_selected';            option_li.id='selected_' + name;            $('select_info_' + name).appendChild(document.createTextNode(option_li.innerHTML));        }                 option_li.onmouseover = function(){    this.className='open_hover';}        option_li.onmouseout = function(){            if(this.id=='selected_' + name){                this.className='open_selected';            }            else {                this.className='open';            }        }              option_li.onclick = new Function("clickOptions("+i+","+n+",'"+selects[i].name+"')");    }} function mouseSelects(name){    var sincn = 'select_info_' + name;     $(sincn).onmouseover = function(){ if(this.className=='tag_select') this.className='tag_select_hover'; }    $(sincn).onmouseout = function(){ if(this.className=='tag_select_hover') this.className='tag_select'; }     if (isIE){        $(sincn).onclick = new Function("clickSelects('"+name+"');window.event.cancelBubble = true;");    }    else if(!isIE){        $(sincn).onclick = new Function("clickSelects('"+name+"');");        $('select_info_' +name).addEventListener("click", stopBubbling, false);    } } function clickSelects(name){    var sincn = 'select_info_' + name;    var sinul = 'options_' + name;         for (i=0;i<selects.length;i++){            if(selects[i].name == name){                            if( $(sincn).className =='tag_select_hover'){                $(sincn).className ='tag_select_open';                $(sinul).style.display = '';            }            else if( $(sincn).className =='tag_select_open'){                $(sincn).className = 'tag_select_hover';                $(sinul).style.display = 'none';            }        }        else{            $('select_info_' + selects[i].name).className = 'tag_select';            $('options_' + selects[i].name).style.display = 'none';        }    } } function clickOptions(i, n, name){            var li = $('options_' + name).getElementsByTagName('li');     $('selected_' + name).className='open';    $('selected_' + name).id='';    li[n].id='selected_' + name;    li[n].className='open_hover';    $('select_' + name).removeChild($('select_info_' + name));     select_info = document.createElement('div');        select_info.id = 'select_info_' + name;        select_info.className='tag_select';        select_info.style.cursor='pointer';    $('options_' + name).parentNode.insertBefore(select_info,$('options_' + name));     mouseSelects(name);     $('select_info_' + name).appendChild(document.createTextNode(li[n].innerHTML));    $( 'options_' + name ).style.display = 'none' ;    $( 'select_info_' + name ).className = 'tag_select';    selects[i].options[n].selected = 'selected'; } window.onload = function(e) {    bodyclick = document.getElementsByTagName('body').item(0);    rSelects();    bodyclick.onclick = function(){        for (i=0;i<selects.length;i++){                $('select_info_' + selects[i].name).className = 'tag_select';            $('options_' + selects[i].name).style.display = 'none';        }    }}</script></head><body><div id="macstyle1">	<select >		<option  value="GMT-12:00">GMT-12:00 日界线西</option>		<option  value="GMT-11:00">GMT-11:00 中途岛，萨摩亚群岛</option>		<option  value="GMT-10:00">GMT-10:00 夏威夷</option>		<option  value="GMT-9:00">GMT-9:00 阿拉斯加</option>		<option  value="GMT-8:00">GMT-8:00 太平洋时间(美国和加拿大)</option>		<option  value="GMT-7:00">GMT-7:00 山地时间(美国和加拿大)</option>		<option  value="GMT-6:00">GMT-6:00 中部时间(美国和加拿大)</option>		<option  value="GMT-5:00">GMT-5:00 东部时间(美国和加拿大)</option>		<option  value="GMT-4:30">GMT-4:30 加拉斯加</option>		<option  value="GMT-4:00">GMT-4:00 大西洋时间(加拿大)</option>		<option  value="GMT-3:30">GMT-3:30 纽芬兰</option>		<option  value="GMT-3:00">GMT-3:00 乔治郭、巴西利亚</option>		<option  value="GMT-2:00">GMT-2:00 中大西洋</option>		<option  value="GMT-1:00">GMT-1:00 佛得角群岛、亚速尔群岛</option>		<option  value="GMT-0:00">GMT-0:00 都柏林、爱丁堡、伦敦</option>		<option  value="GMT+1:00">GMT+1:00 阿姆斯特丹、柏林、罗马、巴黎</option>		<option  value="GMT+2:00">GMT+2:00 雅典、耶路撒冷、伊斯坦布尔</option>		<option  value="GMT+3:00">GMT+3:00 巴格达、科威特、莫斯科</option>		<option  value="GMT+3:30">GMT+3:30 德黑兰</option>		<option  value="GMT+4:00">GMT+4:00 高加索标准时间</option>		<option  value="GMT+4:30">GMT+4:30 喀布尔</option>		<option  value="GMT+5:00">GMT+5:00 伊斯兰堡、卡拉奇、塔什干</option>		<option  value="GMT+5:30">GMT+5:30 马德拉斯、孟买、新德里</option>		<option  value="GMT+5:45">GMT+5:45 加德满都</option>		<option  value="GMT+6:00">GMT+6:00 阿拉木图、新西伯利亚、达卡</option>		<option  value="GMT+6:30">GMT+6:30 仰光</option>		<option  value="GMT+7:00">GMT+7:00 曼谷、河内、雅加达</option>		<option  value="GMT+8:00" selected="selected">GMT+8:00 北京、乌鲁木齐、新加坡</option>		<option  value="GMT+9:00">GMT+9:00 汉城、东京、大阪、札幌</option>		<option  value="GMT+9:30" >GMT+9:30 阿德莱德、达尔文</option>		<option  value="GMT+10:00" >GMT+10:00 墨尔本、悉尼、堪培拉</option>		<option  value="GMT+11:00">GMT+11:00 马加丹、索罗门群岛</option>		<option  value="GMT+12:00">GMT+12:00 奥克兰、惠灵顿</option>		<option  value="GMT+13:00">GMT+13:00 努库阿洛法</option>	</select></div> </body></html>