表单代码如下:
<form action = "login-in.html" name = "login" id = "login" method = "post">
<table>
<tr>
<td valign = "middle"><img src = "images/login_user.png" alt = "username"></td>
<td valign = "middle"><input type = "text" class = "inputbg" id = "username"></td>
</tr>
<tr>
<td valign = "middle"><img src = "images/login_password.png" alt = "password"></td>
<td valign = "middle"><input type = "password" class = "inputbg" id = "username"></td>
</tr>
<tr>
<td valign = "middle"></td>
<td valign = "middle"><input type = "checkbox" name = "remberP">Rember my password</td>
</tr>
</table>
<input type = "submit" value = "login" id = "lg"/>
</form>js代码如下:function checkLoginInfro(userName,password){
alert("xx");
if(userName == undefined || password == undefined){
alert("userName or password is null !");
return false;
}else{
return false;
}
}
document.getElementById("login").onsubmit = checkLoginInfro();
为什么这么绑定的时候,只在网页加载的时候调用一次就不在有效果了?
<form action = "login-in.html" name = "login" id = "login" method = "post">
<table>
<tr>
<td valign = "middle"><img src = "images/login_user.png" alt = "username"></td>
<td valign = "middle"><input type = "text" class = "inputbg" id = "username"></td>
</tr>
<tr>
<td valign = "middle"><img src = "images/login_password.png" alt = "password"></td>
<td valign = "middle"><input type = "password" class = "inputbg" id = "username"></td>
</tr>
<tr>
<td valign = "middle"></td>
<td valign = "middle"><input type = "checkbox" name = "remberP">Rember my password</td>
</tr>
</table>
<input type = "submit" value = "login" id = "lg"/>
</form>js代码如下:function checkLoginInfro(userName,password){
alert("xx");
if(userName == undefined || password == undefined){
alert("userName or password is null !");
return false;
}else{
return false;
}
}
document.getElementById("login").onsubmit = checkLoginInfro();
为什么这么绑定的时候,只在网页加载的时候调用一次就不在有效果了?
alert("xx");
var userName=document.getElementById('username').value;
var passWordv=document.getElementById('password').value;
if(userName =='' || passWordv =='' ){
alert("userName or password is null !");
return false;
}else{
return true;
}
}
其二(主要):
document.getElementById("login").onsubmit = checkLoginInfro();
你把方法checkLoginInfro()的调用放到js代码中,当然就只能执行一次了。要想每次都执行,需要放到
<form action = "login-in.html" name = "login" id = "login" method = "post" onsubmit="checkLoginInfro()">的onsubmit方法中调用。
有区别的,要不都加上
你就把onsubmit写到form属性里,
然后你就用
var userName=document.getElementById('username').value;
var passWordv=document.getElementById('password').value;
当然先把你2个ID都叫USERNAME改掉一个然后需要userName == undefined || password == undefined
那是你找不到这个对象
表单代码如下:<form action = "login-in.html" name = "login" id = "login" method = "post" onsubmit="return checkLoginInfro();">
<table>
<tr>
<td valign = "middle"><img src = "images/login_user.png" alt = "username"></td>
<td valign = "middle"><input type = "text" class = "inputbg" id = "username"></td>
</tr>
<tr>
<td valign = "middle"><img src = "images/login_password.png" alt = "password"></td>
<td valign = "middle"><input type = "password" class = "inputbg" id = "username"></td>
</tr>
<tr>
<td valign = "middle"></td>
<td valign = "middle"><input type = "checkbox" name = "remberP">Rember my password</td>
</tr>
</table>
<input type = "submit" value = "login" id = "lg"/>
</form>js代码如下:function checkLoginInfro(userName,password){
alert("xx");
if(userName == undefined || password == undefined){
alert("userName or password is null !");
return false;
}else{
return false;
}
}这样就可以在每次提交时进行表单验证了