Solution Using jQuery
<script src="http://code.jquery.com/jquery-2.1.0.min.js"></script>
<style>
#form label{float:left; width:140px;}
#error_msg{color:red; font-weight:bold;}
</style>
<script>
$(document).ready(function(){
var $submitBtn = $("#form input[type='submit']");
var $passwordBox = $("#password");
var $confirmBox = $("#confirm_password");
var $errorMsg = $('<span id="error_msg">Passwords do not match.</span>');
// This is incase the user hits refresh - some browsers will maintain the disabled state of the button.
$submitBtn.removeAttr("disabled");
function checkMatchingPasswords(){
if($confirmBox.val() != "" && $passwordBox.val != ""){
if( $confirmBox.val() != $passwordBox.val() ){
$submitBtn.attr("disabled", "disabled");
$errorMsg.insertAfter($confirmBox);
}
}
}
function resetPasswordError(){
$submitBtn.removeAttr("disabled");
var $errorCont = $("#error_msg");
if($errorCont.length > 0){
$errorCont.remove();
}
}
$("#confirm_password, #password")
.on("keydown", function(e){
/* only check when the tab or enter keys are pressed
* to prevent the method from being called needlessly */
if(e.keyCode == 13 || e.keyCode == 9) {
checkMatchingPasswords();
}
})
.on("blur", function(){
// also check when the element looses focus (clicks somewhere else)
checkMatchingPasswords();
})
.on("focus", function(){
// reset the error message when they go to make a change
resetPasswordError();
})
});
</script>
And update your form accordingly:
<form id="form" name="form" method="post" action="registration.php">
<label for="username">Username : </label>
<input name="username" id="username" type="text" /></label><br/>
<label for="password">Password :</label>
<input name="password" id="password" type="password" /><br/>
<label for="confirm_password">Confirm Password:</label>
<input type="password" name="confirm_password" id="confirm_password" /><br/>
<input type="submit" name="submit" value="registration" />
</form>
This will do precisely what you asked for:
- validate that the password and confirm fields are equal without clicking the register button
- If password and confirm password field will not match it will place an error message at the side of confirm password field and disable registration button
It is advisable not to use a keyup event listener for every keypress because really you only need to evaluate it when the user is done entering information. If someone types quickly on a slow machine, they may perceive lag as each keystroke will kick off the function.
Also, in your form you are using labels wrong. The label element has a "for" attribute which should correspond with the id of the form element. This is so that when visually impaired people use a screen reader to call out the form field, it will know text belongs to which field.