Detailed explanation of how to set the default selection of the select tag

This article mainly shares with you an option method for setting the default selected option of the select tag. It has a good reference value and I hope it can help everyone.

There are two methods.

The first method is to set the selected item through the attribute of . This method can control the output results as needed in the background in dynamic languages ​​such as php.

1 option >
2 option >
3 option >
 select >

The second is to control the selected item through front-end js:

function change(){
  document.getElementById("sel")[2].selected=true;
}
 script >

1 option >
2 option >
3 option >
 select >

The js code to get the text of the selected item in the label is:

var val = document.all.Item.options[document.all.Item.selectedIndex].text
var i=document.getElementById( 'sel' ).options[document.getElementById( 'sel' ).selectedIndex].value;

Some others The techniques for operating the tag are as follows:

1) Dynamically create select

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

2) Add option 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) Delete all options option

function removeAll(){
var obj=document.getElementById( 'mySelect' );
obj.options.length=0;
}

4) Delete an option 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) Get the value of option 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].value;

6) Get the text of option 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].text;

7) Modify option 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) Delete select

function removeSelect(){
var mySelect = document.getElementById( "mySelect" );
mySelect.parentNode.removeChild(mySelect);
}

Related recommendations:

What are the uses of select tags in HTML

JQuery Get the text content of multiple select tag options (example)

Detailed explanation of the method of js getting the value of the select tag

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