Several ways to operate select controls with js_form special effects

1 Determine whether there is an Item with Value="paraValue" in the select option
2 Add an Item to the select option
3 Delete an Item from the select option
4 Delete the selected item in the select
5 Modify the text of value="paraValue" in the select option to "paraText"
6 Set the first Item of text="paraText" in the select to be selected
7 Set the Item of value="paraValue" in the select to be selected
8 Get the value of the currently selected item of select
9 Get the text of the currently selected item of select
10 Get the Index of the currently selected item of select
11 Clear the selected item

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

js code
// 1. Determine whether there is an Item with Value="paraValue" in the select option
function jsSelectIsExitItem(objSelect, objItemValue) {
var isExit = false;
for (var i = 0; i if (objSelect.options[i]. value == objItemValue) {
isExit = true;
break;
}
}
return isExit;
}

// 2. Go to the select option Add an Item
function jsAddItemToSelect(objSelect, objItemText, objItemValue) {
//Determine whether it exists
if (jsSelectIsExitItem(objSelect, objItemValue)) {
alert("The Value of the Item already exists ");
} else {
var varItem = new Option(objItemText, objItemValue);
objSelect.options.add(varItem);
alert("Successfully added");
}
}

// 3. Remove an Item from the select option
function jsRemoveItemFromSelect(objSelect, objItemValue) {
//Determine whether it exists
if (jsSelectIsExitItem(objSelect, objItemValue) )) {
for (var i = 0; i if (objSelect.options[i].value == objItemValue) {
objSelect.options.remove (i);
break;
}
}
alert("Deleted successfully");
} else {
alert("This item does not exist in the selection");
}
}


// 4. Delete the selected item 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 text of value="paraValue" in the select option to "paraText"
function jsUpdateItemToSelect(objSelect, objItemText, objItemValue) {
//Determine whether it exists
if (jsSelectIsExitItem(objSelect, objItemValue)) {
for (var i = 0; i if (objSelect.options[i ].value == objItemValue) {
objSelect.options[i].text = objItemText;
break;
}
}
alert("Successfully modified");
} else {
alert("This item does not exist in the selection");
}
}

// 6. Set the first Item of text="paraText" in the select to Select
function jsSelectItemByValue(objSelect, objItemText) {
//Determine whether it exists
var isExit = false;
for (var i = 0; i if (objSelect.options[i].text == objItemText) {
objSelect.options[i].selected = true;
isExit = true;
break;
}
}
//Show the result
if (isExit) {
alert("Successfully selected");
} else {
alert("This item does not exist in the selection");
}
}

// 7. Set the Item with value="paraValue" in the select to be selected
function check(){
var c = document.all.objSelect;
for (var i=0;iif (c.options(i).value==paraValue){
c.selectedIndex =i;
}
}
}


// 8. Get the value of the currently selected item of select
var currSelectValue = document.all.objSelect.value;

// 9. Get the text of the currently selected item of select
var currSelectText = document.all.objSelect.options[document.all.objSelect.selectedIndex].text;

// 10. Get the select Index of the currently selected item
var currSelectIndex = document.all.objSelect.selectedIndex;

// 11. Clear the selected item
document.all.objSelect.options.length = 0;