匿名用户
1级
-11-16 回答
第一种通过的属性来设置选中项，此方法可以在动态语言如php在后台根据需要控制输出结果。
< select id = "sel" >
< option value = "1" >1 option >
< option value = "2" selected = "selected" >2 option >
< option value = "3" >3 option >
select >
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第二种为通过前端js来控制选中的项:
< script type = "text/javascript" >
function change(){
document.getElementById("sel")[2].selected=true;
}
script >
< select id = "sel" >
< option value = "1" >1 option >
< option value = "2" >2 option >
< option value = "3" >3 option >
select >
< input type = "button" value = "修改" onclick = "change()" />
获取标签选中项文本的js代码为:
================
var val = document.all.Item.options[document.all.Item.selectedIndex].text
var i=document.getElementById( ‘sel‘ ).options[document.getElementById( ‘sel‘ ).selectedIndex].value;
一些其它操作标签的技巧如下：
1)动态创建select
================
function createSelect(){
var mySelect = document.createElement( "select" );
mySelect.id = "mySelect" ;
document.body.appendChild(mySelect);
}
2)添加选项option
================
function addOption(){
//根据id查找对象，
var obj=document.getElementById( ‘mySelect‘ );
//添加一个选项
obj.add( new Option( "文本" , "值" ));
}
3)删除所有选项option
================
function removeAll(){
var obj=document.getElementById( ‘mySelect‘ );
obj.options.length=0;
}
4)删除一个选项option
================
function removeOne(){
var obj=document.getElementById( ‘mySelect‘ );
//index,要删除选项的序号，这里取当前选中选项的序号
var index=obj.selectedIndex;
obj.options.remove(index);
}
5)获得选项option的值
================
var obj=document.getElementById( ‘mySelect‘ );
var index=obj.selectedIndex; //序号，取当前选中选项的序号
var val = obj.options[index].value;
6)获得选项option的文本
================
var obj=document.getElementById( ‘mySelect‘ );
var index=obj.selectedIndex; //序号，取当前选中选项的序号
var val = obj.options[index].text;
7)修改选项option
================
var obj=document.getElementById( ‘mySelect‘ );
var index=obj.selectedIndex; //序号，取当前选中选项的序号
var val = obj.options[index]= new Option( "新文本" , "新值" );
8)删除select
================
function removeSelect(){
var mySelect = document.getElementById( "mySelect" );
mySelect.parentNode.removeChild(mySelect);
}
