js正则表达式判断大小写

<div>
    <input type="text" name="textfield" id="sourceString">
    <input type="text" name="textfield" id="resultString">
div>
<div>
    <input type="button" name="button" id="button1" value="转换为小写"οnclick="changeToL()">
    <input type="button" name="button" id="button2" value="转换为大写"οnclick="changeToU()">
    <input type="button" name="button" id="button3" value="判断转换为大小写"οnclick="textToLorU()">
div>
<script>
    function  ToL(str)
    {
      str= str.toLowerCase();
        return str;
    }
    function  ToU(str)
    {
        str= str.toUpperCase();
        return str;
    }
    function textToLorU(){
        var str=document.getElementById("sourceString").value;
        if(/^[0-9A-Z]*$/.test(str)){
               alert("全是大写");
        }else if (/^[0-9a-z]*$/.test(str)){
               alert("全是小写");
        }else{
             alert("其中有大写有小写");
        }
    }
    function changeToL(){
        var str=document.getElementById("sourceString").value;
        str= ToL(str);
        var ID=document.getElementById("resultString");
        ID.value=str;
    }
    function changeToU(){
        var str=document.getElementById("sourceString").value;
        str= ToU(str);
        var ID=document.getElementById("resultString");
        ID.value=str;
    }

script>