<select> tags in html How to set options that are selected by default

There are two ways of doing this.

The first is to set the selected item through the <select> property, which can control the output as needed in a dynamic language such as PHP in the background.

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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   ;

The second is to control the selected item by the front-end JS: Compiled by www.169it.com

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<scripttype="text/javascript">function change(){    document.getElementById("sel")[2].selected=true;}</script><selectid= "sel" ><optionvalue="1">1</option><optionvalue="2">2</option><optionvalue="3">3</option></select><inputtype="button"value="修改"onclick="change()" />

Get <select> Tag The text of the selected item is JS code:

12	varval = document.all.Item.options[document.all.Item.selectedIndex].textvar  i=document.getElementById( ‘sel‘ ).options[document.getElementById( ‘sel‘).selectedIndex].value;

Some other tips for handling <select> labeling are as follows:

1) Dynamically Create Select

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functioncreateSelect(){var  mySelect = document.createElement( "select" );mySelect.id =  "mySelect";document.body.appendChild(mySelect);}

2) Add Options option

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functionaddOption(){//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) Remove all options option

1234	functionremoveAll(){var  obj=document.getElementById( ‘mySelect‘);obj.options.length=0;}

4) Delete an option

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functionremoveOne(){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varindex=obj.selectedIndex;obj.options.remove(index);}

5) Get the value of option options

123	varobj=document.getElementById( ‘mySelect‘ );var index=obj.selectedIndex;  //序号，取当前选中选项的序号varval = obj.options[index].value;

6) to get the text of options option

123	varobj=document.getElementById( ‘mySelect‘ );var index=obj.selectedIndex;  //序号，取当前选中选项的序号varval = obj.options[index].text;

7) Modify Options option

123	varobj=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) Delete Select

1234	functionremoveSelect(){var  mySelect = document.getElementById( "mySelect");mySelect.parentNode.removeChild(mySelect);}

<select> tags in html How to set options that are selected by default