How to set the default selected option based on the select tag?-JS Tutorial-php.cn

Below I will share with you an article on how to set the default selected option for the select tag. It has a good reference value and I hope it will be helpful to everyone.

There are two methods.

##The first sets the selected item through the attribute of . This method can be used in dynamic languages such as php in the background according to Need to control the output results.

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

function change(){ document.getElementById("sel")[2].selected=true; } 1 2 3 Copy after login

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

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

Some other 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); } Copy after login

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" )); } Copy after login

3) Delete all options option

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

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); } Copy after login

5) Get the value of 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; Copy after login

6) Get the text of 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; Copy after login

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" ); Copy after login

8) Delete select

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

The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.