网上看到很不错的阻止form空表单提交
第一种方法
<div class="warp">
<h2>登录到pfan空间</h2>
<p>这里有更多的知识分享，交流。</p>
<form action="/register" method = "post" >
<input type="text" name = "username" placeholder = "请输入注册用户名"> <br />
<input type="password" name = "pwd" placeholder = "请输入初始密码"> <br />
<input type="password" name = "aginpwd" placeholder = "请再次输入密码"> <br />
<input type="submit" value ="注册" class="login_btn">
</form>
</div>
<script>
var form = document.forms[0],
submit = document.querySelector(".login_btn"),
inputBtn = document.getElementsByTagName("input");
console.log(form);
form.onsubmit = function(){
if(inputBtn[0].value == ""){
alert("请您认真填写注册用户名！");
return false;
}else if(inputBtn[1].value == ""){
alert("请您认真输入初始密码！");
return false;
}else if(inputBtn[2].value == ""){
alert("请您再次输入密码");
return false;
}else if(inputBtn[1].value != inputBtn[2].value){
alert("两次密码输入不匹配，请更正！");
return false;
} }
</script>
第二种
<div class="warp">
<h2>登录到pfan空间</h2>
<p>这里有更多的知识分享，交流。</p>
<form action="/register" method = "post" >
<input type="text" name = "username" placeholder = "请输入注册用户名"> <br />
<input type="password" name = "pwd" placeholder = "请输入初始密码"> <br />
<input type="password" name = "aginpwd" placeholder = "请再次输入密码"> <br />
<input type="submit" value ="注册" class="login_btn">
</form>
</div>
<script>
var form = document.forms[0],
submit = document.querySelector(".login_btn"),
inputBtn = document.getElementsByTagName("input");
console.log(form);
form.addEventListener("submit",function(e){
if(inputBtn[0].value == ""){
alert("请您认真填写注册用户名！");
e.preventDefault();
}else if(inputBtn[1].value == ""){
alert("请您认真输入初始密码！");
e.preventDefault();
}else if(inputBtn[2].value == ""){
alert("请您再次输入密码");
e.preventDefault();
}else if(inputBtn[1].value != inputBtn[2].value){
alert("两次密码输入不匹配，请更正！");
e.preventDefault();
}
},false); </script>
参考：http://www.cnblogs.com/pingfan1990/p/4655233.html