JS Operation select dropdown box dynamic change

1. Create a Select dynamically

function Createselect () {

var myselect = document.createelement_x ("select");

myselect.id = "Myselect";

document.body.appendChild ( Myselect);

   }

2. Add Options option

function AddOption ( ) {

// find objects based on IDs,

var obj= document.getelementbyidx_x (' Myselect ');

/ / Add an option

obj.add ( new   Option ("text", "value") );  

  }

3. Delete all options option

function RemoveAll ( ) {

var obj= document.getelementbyidx_x (' Myselect ');

obj.options.length=0 ;

  }

4. Delete an option

function Removeone () {

var obj=document.getelementbyidx_x (' Myselect ');

//index , to remove the ordinal number of the option, This takes the number of the currently selected option

var index= Obj.selectedindex;

obj.options.remove (  index);

  }

5. Get the value of options option

var obj=document.getelementbyidx_x (' Myselect ');

var Index=obj.selectedindex; Ordinal number, taking the number of the currently selected option

var val = obj.options[index].value;

6. Get Options Option text

var obj=document.getelementbyidx_x (' Myselect ');

var Index=obj.selectedindex; Ordinal number, taking the number of the currently selected option

var val = obj.options[index].text;

7. Modify Options option

var obj=document.getelementbyidx_x (' Myselect ');

var Index=obj.selectedindex; Ordinal number, taking the number of the currently selected option

var val = obj.options[index]=new Option ("New text", "New value");

8. Delete Select

function Removeselect () {

var myselect = document.gete Lementbyidx_x ("Myselect");

MySelect.parentNode.remov Echild (Myselect);

  }