php - javascript form validation doesn't work even though everything seems okay (JS is not disabled in browser) -

i have form:

<form action="../scrapll_m_nonstatic/process/reg/signup_process.php" method="post" name="signup" onsubmit="return signupval()">             <div id="fieldholder">                 <input type="text" id="accountfieldfirstname" class="accountfield" name="firstname" placeholder="first name" />                 <input type="text" id="accountfieldlastname" class="accountfield" name="lastname" placeholder="last name" />                 <input type="text" id="accountfieldusername" class="accountfield" name="username" placeholder="username" />                 <input type="text" id="accountfieldemail" class="accountfield" name="email" placeholder="email address" />                 <input type="password" id="accountfieldpassword" class="accountfield" name="password" placeholder="password" />             </div>             <div id="subfooter">                 <a data-ftrans="slide reverse" href="index.php" id="signupbutton">sign in</a>                 <a data-ftrans="slide" href="forgot.php" id="forgotbutton">forgot password</a>             </div>             <div id="footer">                 <input type="submit" id="signin" value="sign up" />         </form> 

and have js form validation script check if forms empty:

function signupval() {     var firstname = document.forms["signup"]["firstname"].value;     var lastname = document.forms["signup"]["lastname"].value;     var username = document.forms["signup"]["username"].value;     var email = document.forms["signup"]["email"].value;     var password = document.forms["signup"]["password"].value;     if (firstname == null || lastname == "" || lastname == null || lastname == "" ||    username == null || username == "" || email == null || email == "" || password == null || password = "")     {         alert("please fill out form completely");         return false;     } } 

it doesn't , goes directly action php script. how can fix that?

you have 2 mistakes:

1). name of user name input not match in js code. fix this:

<input type="text" name="username" id="accountfieldusername" class="accountfield" placeholder="username" /> 

instead of name="username"

2). check values this:

if (firstname == "" || lastname == "" || username == "" || email == "" || password == "") {     alert("please fill out form completely");     return false; } 

also don't need == null checks because form element value cannot null, it's empty string if left blank.

demo: http://jsfiddle.net/tn4a6/