html> 
 head> 
  script type="text/javascript"> 
   function show() 
   { 
    //彈出一個(gè)提示框 
    window.alert("hh"); 
   } 
   //將show方法綁定到按鈕上 
   window.onload=function() 
   { 
    //定位到按鈕 
    var buttonElement=document.forms[0].mybtn; 
    //動(dòng)態(tài)綁定show方法 
    buttonElement.onclick=show; 
    //show如果加()則一加載網(wǎng)頁(yè)就彈出提示框 
   } 
   function validateForm() 
   { 
    var loginform=document.forms[1]; 
    var username=trim(loginform.username.value); 
    var password=trim(loginform.password.value); 
    var email=trim(loginform.email.value); 
//    alert("替代前長(zhǎng)度："+username.length); 
//    username=trim(username); 
 //   alert("替代后長(zhǎng)度："+username.length); 
    //判斷用戶名必填： 
    if(username.length==0) 
    { 
     alert("用戶必填"); 
    } 
    else if(!/^[a-zA-Z0-9]+$/.test(username)) 
    { 
     alert("用戶名必須是英文字母"); 
    } 
    else if(password.length==0) 
    { 
     alert("密碼必填"); 
    } 
    else if(!/^[0-9]{6}$/.test(password)) 
    { 
     alert("密碼必須為6位數(shù)字"); 
    } 
    else if(email.length==0) 
    { 
     alert("郵箱必填"); 
    } 
    else if(!/^\w+@\w+(\.\w+)+$/.test(email)) 
    { 
     alert("郵箱格式不正確"); 
    } 
    return false; 
   } 
   //自定義一個(gè)去空格的參數(shù) 
   function trim(s) 
   { 
    //s.REPLACE(正則表達(dá)式,替換的字符) 
    s=s.replace(/^\s*$/,""); 
    return s; 
   } 
  /script> 
  style type="text/css"> 
   .myclass{ 
    position: absolute; 
    left: 400px; 
    top: 150px; 
   } 
  /style> 
 /head>  
 body> 
  div class="myclass"> 
  form action="#" name="myform" method="post"> 
  input type="button" value="單機(jī)" name="mybtn"/> 
  /form> 
  /div> 
  !--登錄頁(yè)面的表單--> 
  form action="#" name="loginform" method="post" onsubmit="return validateForm()"> 
  table border="1" align="center"> 
   caption>基于js的驗(yàn)證/caption> 
    tr> 
     th>用戶名：/th> 
     td>input type="text" name="username"/>/td> 
    /tr> 
    tr> 
     th>密碼：/th> 
     td>input type="password" name="password"/>/td> 
    /tr> 
    tr> 
     th>郵箱：/th> 
     td>input type="text" name="email"/>/td> 
    /tr> 
    tr> 
     td align="center" colspan="2"> 
      input type="submit" value="提交" /> 
     /td> 
    /tr> 
  /table> 
  /form> 
 /body> 
/html>