<script language="javascript" type="text/javascript">
function jinzhi_chg(){
    var num=document.getElementById("in").value;
    var type=document.getElementById("type");
    var tynum,to;
    for(var i=0;i<type.length;i++){ 
        if(type[i].selected)
        tynum=parseInt(type[i].value);
    }
    switch(tynum){
        case(1):to=parseInt(num).toString(2);break;
        case(2):to=parseInt(num).toString(8);break;
        case(3):to=parseInt(num).toString(16);break;
        case(4):to=parseInt(num,2);break;
        case(5):to=parseInt(num,8);break;
        case(6):to=parseInt(num,16);break;
        case(7):to=parseInt(num,2).toString(8);break; 
        case(8):to=parseInt(num,8).toString(2);break; 
        case(9):to=parseInt(num,2).toString(16);break; 
        case(10):to=parseInt(num,16).toString(2);break; 
        case(11):to=parseInt(num,8).toString(16);break; 
        case(12):to=parseInt(num,16).toString(8);break; 
    }
    document.getElementById("out").value=to;
}
</script>
<select name="type" id="type">
    <option value="1">十进制转二进制</option>
    <option value="2">十进制转八进制</option>
    <option value="3">十进制转十六进制</option>
    <option value="4">二进制转十进制</option>
    <option value="5">八进制转十进制</option>
    <option value="6">十六进制转十进制</option>
    <option value="7">二进制转八进制</option>
    <option value="8">八进制转二进制</option>
    <option value="9">二进制转十六进制</option>
    <option value="10">十六进制转二进制</option>
    <option value="11">八进制转十六进制</option>
    <option value="12">十六进制转八进制</option>
</select>
输入值：<input type="text" id="in" />
输出值：<input type="text" id="out" disabled="disabled" />
<input type="button" value="开始转换" onclick="jinzhi_chg()" />