A complete list of Javascript select control operations (add, modify, delete, select, clear, determine existence, etc.)_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. Add an Item to the select option
function jsAddItemToSelect(objSelect, objItemText, objItemValue) {
//Determine whether it exists
if (jsSelectIsExitItem(objSelect , objItemValue)) {
alert("The Value of this Item already exists");
} else {
var varItem = new Option(objItemText, objItemValue);
objSelect.options.add( varItem);
alert("Successfully added");
}
}
// 3. Delete 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("Successfully deleted");
} else {
alert("This item does not exist in the select");
}
}
// 4. Delete the selected item in the 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 select");
}
}
// 6. Set the first position of text="paraText" in the select An Item is selected
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("The item does not exist in the selection ");
}
}
// 7. Set the Item with value="paraValue" in the select to be selected
document.all.objSelect.value = objItemValue;
// 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 Index of the currently selected item of select
var currSelectIndex = document.all.objSelect.selectedIndex;
// 11. Clear the select Items of
document.all.objSelect.options.length = 0;