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var firstoptionlen=firstoptionelems.length

2013-02-19

var firstoptionlenfirstoptionelems.lengthhtmlheadmeta http-equivContent-Type contenttex

var firstoptionlen=firstoptionelems.length;
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>

<style type="text/css">

</style></head>

<body>

<div style="border:1px dashed #E6E6E6;margin:150px 0px 0px 450px; width:350px; height:200px; background-color:#E6E6E6;">
<table width="285" height="169" border="0" align="left" cellpadding="0" cellspacing="0" style="margin:15px 0px 0px 15px;">
<tr>
<td width="126">

<select name="first" multiple="multiple" size=10 class="td3" id="first">
<option value="选项1">选项1</option>
<option value="选项2">选项2</option>
<option value="选项3">选项3</option>
<option value="选项4">选项4</option>
<option value="选项5">选项5</option>
<option value="选项6">选项6</option>
<option value="选项7">选项7</option>
<option value="选项8">选项8</option>
</select>
</td>
<td width="69" valign="middle">
<input name="add" id="add" type="button" class="button" value="-->" />
<input name="add_all" id="add_all" type="button" class="button" value="==>" />
<input name="remove" id="remove" type="button" class="button" value="<--" />
<input name="remove_all" id="remove_all" type="button" class="button" value="<==" />
</td>
<td width="127" align="left">
<select name="second" size="10" multiple="multiple" class="td3" id="second">
<option value="选项9">选项9</option>
</select>
</td>
</tr>
</table>
</div>
</body>
<script type="text/javascript">

//1 获取左边的下拉选框
var firstelement=document.getElementById("first");
//2 获取左边的所有option

var firstoptionelems=firstelement.getElementsByTagName("option");
var firstoptionlen=firstoptionelems.length;

var secondelem=document.getElementById("second");
var secondoptionelems=secondelem.getElementsByTagName("option");
var seconoptionlen=secondoptionelems.length;

// alert("tfy");
//<input name="add" id="add" type="button" class="button" value="-->" />
document.getElementById("add").onclick=function (){

for (var i=0;i<firstoptionlen;i++){
/*
* selectedIndex属性：
* * 如果没有选择任意一个选项，selectedIndex属性的值是"-1"
* * 如果选中一个选项时，selectedIndex属性的值是被选中的选项的索引值
* * 如果选中多个选项时，selectedIndex属性的值是第一个被选中的选项的索引值
*/
if(firstelement.selectedIndex!=-1){
//由于选择的不确定，利用selectedIndex属性的值循环刚刚好
secondelem.appendChild(firstoptionelems[firstelement.selectedIndex]);
}

}
}

//<input name="add_all" id="add_all" type="button" class="button" value="==>" />

document.getElementById("add_all").onclick=function (){
// alert("tfy");
for(var i=0;i<firstoptionlen;i++){
secondelem.appendChild(firstoptionelems[0]);
}
}
//<input name="remove" id="remove" type="button" class="button" value="<--" />
document.getElementById("remove").onclick=function (){
// alert("tfy");
for(var i=0;i<firstoptionlen;i++){
if(secondelem.selectedIndex!=-1){
firstelement.appendChild(secondoptionelems[secondelem.selectedIndex]);
}
}
}
//<input name="remove_all" id="remove_all" type="button" class="button" value="<==" />
document.getElementById("remove_all").onclick=function (){
// alert("tfy");
for(var i=0;i<firstoptionlen;i++){
firstelement.appendChild(secondoptionelems[0]);
}
}
//双击从左到右
firstelement.ondblclick=function (){
// alert("tfy");
for(var i=0;i<firstoptionlen;i++){
secondelem.appendChild(firstoptionelems[firstelement.selectedIndex]);
}
}
secondelem.ondblclick=function (){
// alert("tfy");
for(var i=0;i<seconoptionlen;i++){
firstelement.appendChild(secondoptionelems[secondelem.selectedIndex]);
}
}

</script>
</html>

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