disable form submit button when password does not match - php

Question

I'm trying to figure out where I'm supposed to include a js code where I disable the form submit button when the passwords don't match.
html:
<form name=passform class="form-horizontal-signup" method="post" action="login.php" >
<fieldset>
<legend>Sign Up for MyVibes</legend>
<input type="password" class="input-xlarge" placeholder="Password" name="password" id="password" onKeyUp="verify.check()" />
<input type="password" class="input-xlarge" placeholder="Retype Password" name="repassword" id="repassword" onKeyUp="verify.check()"/></fieldset>
<div id="password_result"> </div><br />
<button type="submit" input name="btnSignUp" id="btnSignUp" class="btn btn-inverse" disabled="disabled"/>Sign Up</button>
</form>
</div>
getting the variables:
<SCRIPT TYPE="text/javascript">
verify = new verifynotify();
verify.field1 = document.passform.password;
verify.field2 = document.passform.repassword;
verify.result_id = "password_result";
verify.match_html = "Passwords match.";
verify.nomatch_html = "Please make sure your passwords match.";
// Update the result message
verify.check();
//
</SCRIPT>
and the function:
function verifynotify(field1, field2, result_id, match_html, nomatch_html) {
this.field1 = field1;
this.field2 = field2;
this.result_id = result_id;
this.match_html = match_html;
this.nomatch_html = nomatch_html;
this.check = function() {
// Make sure we don't cause an error
// for browsers that do not support getElementById
if (!this.result_id) { return false; }
if (!document.getElementById){ return false; }
r = document.getElementById(this.result_id);
if (!r){ return false; }
if (this.field1.value != "" && this.field1.value == this.field2.value) {
r.innerHTML = this.match_html;
$("#btnSignUp").prop("disabled", false);
} else {
r.innerHTML = this.nomatch_html;
$("#btnSignUp").prop("disabled", true);
}
}
}
maybe i misplace where i'm supposed to put the $("#btnSignUp").prop("disabled", true); code?

Answer 1

Try
$("#btnSignUp").attr("disabled", "disabled");

Answer 2

this should works..
if (this.field1.value != "" && this.field1.value == this.field2.value) {
r.innerHTML = this.match_html;
$("#btnSignUp").removeAttr("disabled");
} else {
r.innerHTML = this.nomatch_html;
$("#btnSignUp").attr("disabled", "disabled");
}