var t = document.getElementById("select1");
var selectValue=t.options[t.selectedIndex].value;//获取select的值
var t1 = document.getElementById("select2");
for(i=0;i<t1.length;i++){//给select赋值
if(selectValue==t.options[i].value){
t1.options[i].selected=true
}
}
第二种方法,赋值是一样
<select id="select1" name="select1">
<option value="0">0</option>
<option value="1">1</option>
<option value="2">2</option>
</select>
<input type="button" id="button1" value="submit" οnclick="getSelectValue()"/>
<script>
function getSelectValue(){
var selectCount = document.getElementById("select1").options;
for(var i = 0 ; i<selectCount.length;i++){
if(selectCount[i].selected){
alert(selectCount[i].value);
}
}
}
</script>