JavaScript表单验证 - 函数未在提交时运行。

问题描述：

I'm currently working on some very basic validation for a form that posts a bunch of information from a web form to an SQL database with a simple PHP script. The PHP script is working fine, and the values are being posted to the database, however the validation I have written appears to be ignored. I've attempted to fix it for a while now and can't see any glaring mistakes, but apologies if it's anything trivial.

HTML:

<form name = "registerForm" method = "POST" onsubmit = "return ValidateRegistration()" action = "createUser.php">
    <p class = "register">Desired Username*</p>
    <p class = "registerDesc">Between 1 and 20 characters long</p>                  
    <input type = "text" name = "username" class = "register">
    <p class = "register">Desired Password*</p>
    <p class = "registerDesc">We won't force securty onto you; between 6 and 255 characters long. No other criteria.</p>
    <input type = "password" name = "password" class = "register">
    <p class = "register">Confirm Password*</p>
    <input type = "password" name = "confirmPassword" class = "register">
    <p class = "register">Email Adress*</p>
    <input type = "text" name = "email" class = "registerEmail">
    <p class = "register">Bio</p>
    <p class = "registerDesc">Extra information such as hobbies, occupation, background information. Maximum 4096 characters. We can do this later.</p>
    <textarea name = "bio" class = "registerBio"></textarea>
    <p><input type = "submit" class = "registerButton" value = "Register"></p>
</form>

JavaScript:

function ValidateRegistration()
{
    //username block
    var username=document.forms["registerForm"]["username"].value;
    if (username==null || username==" ")
    {
        alert("You must provide a username");
        return false;
    }       
    if (username.length>20 || username.length<1)
    {
        alert("Sorry, your username must be between 1 and 20 characters long.");
        return false;
    }
    //etc....
}

答

Exactly your code is working for me:

Created following test.html file and opened in chrome:

<html>
<head>
<script>
function ValidateRegistration()
{
    //username block
    var username=document.forms["registerForm"]["username"].value;
    if (username==null || username==" ")
    {
        alert("You must provide a username");
        return false;
    }       
    if (username.length>20 || username.length<1)
    {
        alert("Sorry, your username must be between 1 and 20 characters long.");
        return false;
    }
    //etc....
}
</script>
</head>
<body>
<form name = "registerForm" method = "POST" onsubmit = "return ValidateRegistration()" action = "createUser.php">
    <p class = "register">Desired Username*</p>
    <p class = "registerDesc">Between 1 and 20 characters long</p>                  
    <input type = "text" name = "username" class = "register">
    <p class = "register">Desired Password*</p>
    <p class = "registerDesc">We won't force securty onto you; between 6 and 255 characters long. No other criteria.</p>
    <input type = "password" name = "password" class = "register">
    <p class = "register">Confirm Password*</p>
    <input type = "password" name = "confirmPassword" class = "register">
    <p class = "register">Email Adress*</p>
    <input type = "text" name = "email" class = "registerEmail">
    <p class = "register">Bio</p>
    <p class = "registerDesc">Extra information such as hobbies, occupation, background information. Maximum 4096 characters. We can do this later.</p>
    <textarea name = "bio" class = "registerBio"></textarea>
    <p><input type = "submit" class = "registerButton" value = "Register"></p>
</form>
</body>
</html>

Submitting an emtpy form alerts:

Sorry, your username must be between 1 and 20 characters long.

答

I would get rid of the return in the onsubmit.

答

Put your code inside try/catch blocks a see what's going on.

try{
  //your code
}catch(er){
  alert(er);
}

答

http://fiddle.jshell.net/hmariod/LRZkR/

<form name = "registerForm" method = "POST"  action = "createUser.php">
    <p class = "register">Desired Username*</p>
    <p class = "registerDesc">Between 1 and 20 characters long</p>                  
    <input type = "text" name = "username" class = "register">
    <p class = "register">Desired Password*</p>
    <p class = "registerDesc">We won't force securty onto you; between 6 and 255 characters long. No other criteria.</p>
    <input type = "password" name = "password" class = "register">
    <p class = "register">Confirm Password*</p>
    <input type = "password" name = "confirmPassword" class = "register">
    <p class = "register">Email Adress*</p>
    <input type = "text" name = "email" class = "registerEmail">
    <p class = "register">Bio</p>
    <p class = "registerDesc">Extra information such as hobbies, occupation, background information. Maximum 4096 characters. We can do this later.</p>
    <textarea name = "bio" class = "registerBio"></textarea>
    <p><input type = "button" onclick="ValidateRegistration();" class = "registerButton" value = "Register"></p>
</form>

function ValidateRegistration(){
    try{
        var username=document.forms["registerForm"]["username"].value;
        if (username.length < 1)
        {
            alert("You must provide a username");
            return;
        }       
        if (username.length>20 || username.length<1)
        {
            alert("Sorry, your username must be between 1 and 20 characters long.");
            return;
        }
        document.forms["registerForm"].submit();
    }catch(er){
         alert(er);
    }
}

答

i think the problem is in your comparing line

if (username==null || username==" ")

which should be

if (username==null || username=="")

i hope it solves your problem. please let me know ;-)

JavaScript表单验证 - 函数未在提交时运行。

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