转自：https://www.cnblogs.com/besty/p/4094951.html
方法有两种。
第一种通过<select>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。
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< select id = "sel" >< option value = "1" >1</ option >< option value = "2" selected = "selected" >2</ option >< option value = "3" >3</ option ></ select > |
第二种为通过前端js来控制选中的项: 由 www.169it.com 搜集整理
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< 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<select>标签选中项文本的js代码为:
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var val = document.all.Item.options[document.all.Item.selectedIndex].textvar i=document.getElementById( 'sel' ).options[document.getElementById( 'sel' ).selectedIndex].value; |
一些其它操作<select>标签的技巧如下：
1)动态创建select
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function createSelect(){var mySelect = document.createElement( "select" );mySelect.id = "mySelect" ;document.body.appendChild(mySelect);} |
2)添加选项option
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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
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function removeAll(){var obj=document.getElementById( 'mySelect' );obj.options.length=0;} |
4)删除一个选项option
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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
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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
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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
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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
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function removeSelect(){var mySelect = document.getElementById( "mySelect" );mySelect.parentNode.removeChild(mySelect);} |