String和验证

来源：互联网发布：北京人少的景点知乎编辑：程序博客网时间：2024/05/18 01:18

<!doctype html>
<html>
   <head>
       <title>String函数(方法)</title>
       <style type="text/css">
           *{
               font-size:40px;
           }
       </style>

       <script type="text/javascript">

           function loadTxt (){
           }
           function showLen (){
               var txt =document.getElementById("txt").value;
               if(txt.length==0){
                   alert("文本框不能为空");
               }
           }
           function showUp (){
               var txt =document.getElementById("txt").value;

               document.getElementById("txt").value = txt.toUpperCase();

           }
           function showLo (){
               var txt =document.getElementById("txt").value;
               txt = txt.toLowerCase();//转小写
               if('a'<txt){
                   alert("字符a小一些");
               }
           }
           function showChar (){
               var txt =document.getElementById("txt").value;
               //通过下标查找字符
               alert(txt.charAt(4));
           }
           function showIndex (){
               var txt =document.getElementById("txt").value;
               alert(txt.indexOf("我",3));
           }
           function showSub (){
               var txt =document.getElementById("txt").value;
               alert(txt.substring(2,2));

           }

       </script>
   </head>

   <body onload="loadTxt()">
       <input type="text" id="txt" ><br />
       <input type="button" value="测试长度" onclick="showLen()">
       <input type="button" value="转大写" onclick="showUp()">
       <input type="button" value="转小写" onclick="showLo()">
       <input type="button" value="获取字符" onclick="showChar()">
       <br />
       <input type="button" value="获取下标" onclick="showIndex()">
       <input type="button" value="截取字符串" onclick="showSub()">
   </body>
</html>

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