1: 选择select时,如何触发? 哪种事件? onchange
2: 如何获取被选中的option的值 ? selectobj.value
3: 动态生成option innerHTML
<select name="add" οnchange="change()"><option value="">请选择</option><option value="0">北京</option><option value="1">安徽</option></select><select name="city" id=""></select><script type="text/javascript">function change() {var area = [ ['朝阳' , '海淀' , '昌平'] , ['淮北','淮南' , '铜陵'] ];var s1 = document.getElementsByName("add")[0];var city = document.getElementsByName('city')[0];if(s1.value=="") {city.innerHTML = '';return;} else {for(var i=0,str='',len=area[s1.value].length;i<len;i++) {str += '<option value='+i+'>'+area[s1.value][i]+'</option>';city.innerHTML = str;}}}</script>
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