JavaScript实现通过select标签跳转网页的方法

<select name="" onchange="javascript:location.href=this.value;">
<option value="https://.jb51." selected="selected" >jb51</option>
<option value="http://.163." >163</option>
<option value="http://.sina." >sina</option>
<option value="http://.sohu." >sohu</option>
</select>

<select name="" onchange="javascript:window.open(this.options[this.selectedIndex].value)">
<option value="https://.jb51." selected="selected" >jb51</option>
<option value="http://.163." >163</option>
<option value="http://.sina." >sina</option>
<option value="http://.sohu." >sohu</option>
</select>

<form name="frm2" action="">
<select name="page2">
<option value="https://.jb51." selected="selected" >jb51</option>
<option value="http://.163." >163</option>
<option value="http://.sina." >sina</option>
<option value="http://.sohu." >sohu</option>
</select>
<input type="button" value="提交" onclick="javascript:location.href=document.frm2.page2.options[document.frm2.page2.selectedIndex].value;"/>
</form>

<form name="frm" action="">
<select name="page">
<option value="https://.jb51." selected="selected" >jb51</option>
<option value="http://.163." >163</option>
<option value="http://.sina." >sina</option>
<option value="http://.sohu." >sohu</option>
</select>
<input type="button" value="提交" onclick="javascript:window.open(document.frm.page.options[document.frm.page.selectedIndex].value)"/>
</form>

<select name="" onchange="self.location.href=options[selectedIndex].value" >
<option value="http://.baidu.">百度</option>
<option value="http://.163.">网易</option>
</select>