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1.判斷select選項(xiàng)中 是否存在value=paravalue地item

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.向select選項(xiàng)中 加入一個(gè)item

function jsadditemtoselect(objselect, objitemtext, objitemvalue) {

//判斷是否存在

if (jsselectisexititem(objselect, objitemvalue)) {

alert(該item地value值已經(jīng)存在);

} else {

var varitem = new option(objitemtext, objitemvalue);

objselect.options.add(varitem);

alert(成功加入);

}

}

// 3.從select選項(xiàng)中 刪除一個(gè)item

function jsremoveitemfromselect(objselect, objitemvalue) {

//判斷是否存在

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(成功刪除);

} else {

alert(該select中 不存在該項(xiàng));

}

}

// 4.刪除select中選中地項(xiàng)

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.修改select選項(xiàng)中 value=paravalue地text為paratext

function jsupdateitemtoselect(objselect, objitemtext, objitemvalue) {

//判斷是否存在

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(成功修改);

} else {

alert(該select中 不存在該項(xiàng));

}

}

// 6.設(shè)置select中text=paratext地第一個(gè)item為選中

function jsselectitembyvalue(objselect, objitemtext) {

//判斷是否存在

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出結(jié)果

if (isexit) {

alert(成功選中);

} else {

alert(該select中 不存在該項(xiàng));

}

}

// 7.設(shè)置select中value=paravalue地item為選中

document.all.objselect.value = objitemvalue;

// 8.的到select地當(dāng)前選中項(xiàng)地value

var currselectvalue = document.all.objselect.value;

// 9.的到select地當(dāng)前選中項(xiàng)地text

var currselecttext = document.all.objselect.options[document.all.objselect.selectedindex].text;

// 10.的到select地當(dāng)前選中項(xiàng)地index

var currselectindex = document.all.objselect.selectedindex;

// 11.清空select地項(xiàng)

document.all.objselect.options.length = 0;

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