表单提交时js页面不刷新判断输入是否为空

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表单：给表单加上

onsubmit="return submitCheck();"

<form action="index.php" method="post" onsubmit="return submitCheck();">
		<table>
		<tr>
			<td>用户名：</td>
			<td><input type="text" id="name" name="name" placeholder="请输入用户名" class="txt"></td>
		</tr>
		<tr>
			<td>密   码：</td>
			<td><input type="password" id="pwd" name="pwd" placeholder="请输入密码" class="txt"></td>
		</tr>
		<tr>
			<td>验证码：</td>
			<td>
				<input type="text" id="yzm" name="yzm" size="10" placeholder="请输入验证码" class="yzm">
                <img id="code" class="img_yzm" src="./public/common/yanzhengma.php" onclick="this.src+='?'"/> </td>
		</tr>
		<tr>
			<td colspan="2"><center><input type="radio" value="普通用户" name="sf" checked="checked"/>普通用户
			  <input type="radio" value="管理员" name="sf"/>管理员</center></td>
		</tr>
		<tr>
			<td colspan="2"><center>
				<input type="submit" name="login" value="登录" class="btn" id="btn1">
				<input type="reset" name="ret" value="重置" class="btn" id="btn2">
			</center></td>
		</tr>
		</table>
	</form>

js页面不刷新判断输入是否为空：

<script type="text/javascript">
// 表单元素提交时ＪＳ判断输入的值，为空时则不刷新页面返回，不为空跳转并传值到新页面
 function submitCheck(){
 	var txt1 = document.getElementById("name");
 	var txt2 = document.getElementById("pwd");
    var txt3 = document.getElementById("yzm");
    if(txt1.value==""){
    	alert("请输入用户名！");
	    txt1.focus();
	    return false;  
    }else if(txt2.value==""){
    	alert("请输入密码！");
	    txt2.focus();
	    return false;  
    }else if(txt3.value==""){
    	alert("请输入验证码！");
	    txt3.focus();
	    return false;  
    }
    return true;
  }
</script>