Javascript²Ù×÷select¿Ø¼þ´óÈ«

1ÅжÏselectÑ¡ÏîÖРÊÇ·ñ´æÔÚValue="paraValue"µÄItem 
 2ÏòselectÑ¡ÏîÖР¼ÓÈëÒ»¸öItem 
 3´ÓselectÑ¡ÏîÖРɾ³ýÒ»¸öItem 
 4ɾ³ýselectÖÐÑ¡ÖеÄÏî 
 5ÐÞ¸ÄselectÑ¡ÏîÖРvalue="paraValue"µÄtextΪ"paraText" 
 6ÉèÖÃselectÖÐtext="paraText"µÄµÚÒ»¸öItemΪѡÖР
 7ÉèÖÃselectÖÐvalue="paraValue"µÄItemΪѡÖР
 8µÃµ½selectµÄµ±Ç°Ñ¡ÖÐÏîµÄvalue 
 9µÃµ½selectµÄµ±Ç°Ñ¡ÖÐÏîµÄtext 
10µÃµ½selectµÄµ±Ç°Ñ¡ÖÐÏîµÄIndex 
11Çå¿ÕselectµÄÏî 
 // 1.ÅжÏselectÑ¡ÏîÖÐ ÊÇ·ñ´æÔÚValue="paraValue"µÄItem
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.ÏòselectÑ¡ÏîÖÐ ¼ÓÈëÒ»¸öItem
function jsAddItemToSelect(objSelect, objItemText, objItemValue) {
//ÅжÏÊÇ·ñ´æÔÚ
if (jsSelectIsExitItem(objSelect, objItemValue)) {
alert("¸ÃItemµÄValueÖµÒѾ­´æÔÚ");
} else {
var varItem = new Option(objItemText, objItemValue);
objSelect.options.add(varItem);
alert("³É¹¦¼ÓÈë");
}
}

// 3.´ÓselectÑ¡ÏîÖРɾ³ýÒ»¸öItem
function jsRemoveItemfromSelect(objSelect, objItemValue) {
//ÅжÏÊÇ·ñ´æÔÚ
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("³É¹¦É¾³ý");
} else {
alert("¸ÃselectÖÐ ²»´æÔÚ¸