JS Dynamic Change Select Select to change the index value of option

document.getElementById ("louyuming"). Options[0].selected=true;

function Jsselectisexititem (Objselect, Objitemvalue) {
var isexit = false;
for (var i = 0; i < objSelect.options.length; i++) {
if (Objselect.options[i].value = = Objitemvalue) {
Isexit = true;
Break
}
}
return isexit;
}

The Javascript action Select is a common form of today, when you delete multiple select values, there is a problem, for half a day the original is caused by the index (that is, the deletion of the time to delete from the beginning of the index, and then delete the index small, otherwise deleted the index small index after the big index changes, There is a problem when you delete it--the key is for the for loop to be from big to small, not regular from 0 to length.

//4. Delete selected items in select     
function Jsremoveselecteditemfromselect (objselect) {   &NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP
     var length = objselect.options.length-1;  &NBSP;&NBSP;&NBSP
     for (var i = length; I >= 0; i--) {    
 & nbsp;       if (objselect[i].selected = = true) {    
              Objselect.options[i] = null;    &NBSP
        }    
     }&NBSP;&NBSP;&NBSP;&NBSP
}      

1 To determine if there is a value= "Paravalue" Item in the Select option
2 Add an item to the Select option
3 Delete an item from the Select option
4 Delete selected Items in select
5 Modify the Select option Value= "Paravalue" text is "Paratext"
6 Set the first item of text= "Paratext" in the Select to select
7 Set the item in the Select Value= "Paravalue" to select
8 Gets the value of the currently selected item of select
9 Gets the text of the currently selected item for select
10 gets the index of the current selected item of select
11 Empty A Select item

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To delete all options in a select dynamically:
function Deletealloptions (SEL) {
sel.options.length=0;
}
To delete an option in a select dynamically:
function Deleteoption (sel,indx) {
Sel.options.remove (INDX);
}
Dynamically add items in Select option:
function AddOption (sel,text,value) {
Sel.options.add (New Option (Text,value));
}
Above in IE and Firefox can be tested successfully, I hope that can be used later.

===========================================

JS Code
1. Determine if there is a value= "Paravalue" Item in the Select option
function Jsselectisexititem (Objselect, Objitemvalue) {
var isexit = false;
for (var i = 0; i < objSelect.options.length; i++) {
if (Objselect.options[i].value = = Objitemvalue) {
Isexit = true;
Break
}
}
return isexit;
}

2. Add an item to the Select option
function Jsadditemtoselect (Objselect, Objitemtext, Objitemvalue) {
To determine whether there is
if (Jsselectisexititem (Objselect, Objitemvalue)) {
Alert ("The value of the item already exists");
} else {
var varitem = new Option (Objitemtext, Objitemvalue);
ObjSelect.options.add (Varitem);
Alert ("Join successfully");
}
}

3. Remove an item from the Select option
function Jsremoveitemfromselect (Objselect, Objitemvalue) {
To determine whether there is
if (Jsselectisexititem (Objselect, Objitemvalue)) {
for (var i = 0; i < objSelect.options.length; i++) {
if (Objselect.options[i].value = = Objitemvalue) {
ObjSelect.options.remove (i);
Break
}
}
Alert ("Successful deletion");
} else {
Alert ("The item does not exist in the select");
}
}


4. Delete selected items in select
function Jsremoveselecteditemfromselect (objselect) {
var length = objselect.options.length-1;
for (var i = length; I >= 0; i--) {
if (objselect[i].selected = = True) {
Objselect.options[i] = null;
}
}
}

5. Modify the Select option Value= "Paravalue" text is "Paratext"
function Jsupdateitemtoselect (Objselect, Objitemtext, Objitemvalue) {
To determine whether there is
if (Jsselectisexititem (Objselect, Objitemvalue)) {
for (var i = 0; i < objSelect.options.length; i++) {
if (Objselect.options[i].value = = Objitemvalue) {
Objselect.options[i].text = Objitemtext;
Break
}
}
Alert ("Successful modification");
} else {
Alert ("The item does not exist in the select");
}
}

6. Set the first item of text= "Paratext" in Select to select
function Jsselectitembyvalue (Objselect, Objitemtext) {
To determine whether there is
var isexit = false;
for (var i = 0; i < objSelect.options.length; i++) {
if (Objselect.options[i].text = = Objitemtext) {
Objselect.options[i].selected = true;
Isexit = true;
Break
}
}
Show the results
if (isexit) {
Alert ("Successfully selected");
} else {
Alert ("The item does not exist in the select");
}
}

7. Set the item of value= "Paravalue" in Select to select
Objselect.value = Objitemvalue;

8. Value of the current selected item of the Select
var currselectvalue = Objselect.value;

9. Gets the text of the currently selected item of select
var currselecttext = Objselect.options[document.all.objselect.selectedindex].text;

10. Index of the current selected item for select
var currselectindex = Objselect.selectedindex;

11. Empty a Select item
objSelect.options.length = 0;

The complete code for the entire instance is as follows: <!doctype HTML PUBLIC "-//W3C//DTD HTML 4.0 transitional//en" >
<title>javascript Select options Text value</title>
<meta name= "keywords" content= "javascript Select options text value add modify delete Set" >
<meta name= "description" content= "JavaScript Select options text value add modify delete Set" >
<script language= "JavaScript" >
<!--
author:i@lxl.cn
Modify:i@cnlei.com
function Watch_ini () {//Initial
for (var i=0; i<arguments.length; i++) {
var ooption=new Option (Arguments[i],arguments[i]);
document.getElementById ("Myselect") [I]=ooption;
}
}
function Watch_add (f) {//Increase
var ooption=new Option (F.word.value,f.word.value);
F.keywords[f.keywords.length]=ooption;
}
function Watch_sel (f) {//Edit
F.word.value = F.keywords[f.keywords.selectedindex].text;
}
function Watch_mod (f) {//Modify
F.keywords[f.keywords.selectedindex].text = F.word.value;
}
function Watch_del (f) {//delete
F.keywords.remove (F.keywords.selectedindex);
}
function Watch_set (f) {//Save
var set = "";
for (var i=0; i<f.keywords.length; i++) {
Set + + F.keywords[i].text + ";";
}
Confirm (set);
}
-->
</script>
<body>
<form name= "Watch" method= "post" action= "" >
<select id= "myselect" name= "keywords" size= "ten" onchange= "Watch_sel" (this.form) "></select><br>
<script language= "JavaScript" >
<!--
Watch_ini ("I", "You", "You", "he", "she", "it", "er"); Initial keywords
-->
</script>
<input type= "text" name= "word"/><br/>
<input type= "button" value= "Add" onclick= "Watch_add (this.form);"/>
<input type= "button" value= "Modify" onclick= "Watch_mod (this.form);"/>
<input type= "button" value= "delete" onclick= "Watch_del (this.form);"/>
<input type= "button" value= "Save" onclick= "Watch_set (this.form);"/>
</form>
</body>