How to wait for ajax validation to complete before submitting a form?

Question

Having a problem where the form submits before the validateUsername function has a chance to complete the username check on the server-side.

How do I submit the form only after the validateUsername function completes? Hope this is clear...

form.submit(function(){
    if (validateUsername() & validateEmail() & validatePassword()) {
        return true;
    } else {
        return false;
    }
});         

function validateUsername(){            
    usernameInfo.addClass("sign_up_drill");
    usernameInfo.text("checking...");
    var b = username.val();
    var filter = /^[a-zA-Z0-9_]+$/;     
    $.post("../username_check.php",{su_username:username.val()},function(data) {
        if (data=='yes') {
            username.addClass("error");
            usernameInfo.text("sorry, that one's taken");
            usernameInfo.addClass("error");
            return false;           
        } else if (!filter.test(b)) {
            username.addClass("error");
            usernameInfo.text("no funny characters please");
            usernameInfo.addClass("error");
            return false;   
        } else {
            username.removeClass("error");
            usernameInfo.text("ok");
            usernameInfo.removeClass("error");      
            return true;    
        }
    });             
}   

Answer 1

More verbose version of Olafur's answer - The AJAX call is made and the function returns without waiting.

The callback doesn't finish until you've submitted the form.

What you should do is have the button/trigger calling the AJAX validation, and the callback should submit the form instead of returning true.

Answer 2

The jQuery form validation plugin takes care of this for you -- I highly recommend it.

Some sample code:

$("#myform").validate({
  rules: {
    email: {
      required: true,
      email: true
    },
    username: {
      required: true,
      remote: {
        url: "../username_check.php",
        type: "post",
        }
      }
    }
  }
});

Answer 3

I dealt with a similar issue recently. Under some circumstances, pressing enter on an input field might make the form submit. I attempted to remedy this in a number of ways, and then the specifications required changed so that pressing the Enter key or Go on a device, will allow a form submission. My solution was just what made sense to me at the time.

var form_submit = false;

function validateInput () {

    var field_value = $('#username').val();

    $.post('validation.php', {'input': field_value }, function (d) {
        if (d.valid) {

            form_submit = true;
            $('form').submit();

        } else {

            //error message or whatever

        }
    }, 'json');

}

$('form').submit( function () {

    if ( form_submit ) {
        return true; 
    } else {
        validateInput();
        return false;
    }

});