Login and register in just one page using php and ajax

I'm working on a project. (web)

The first version, has a separate login.php and register.php which login calls a .js to do an ajax validation. the same happends with register.

The second version, the page have a login and register form in just one page like this:

Login and register in one page

The problem is in this new page version, I import (

(for better understanding, In the image enclosed yellow)

My first idea was put a code to ejecute every .js separate(one .js for login and one .js for register). like this:

if( $_POST['submit_login'] ) {
 echo "<script src='js/login.js'></script>";
}
else if( $_POST['submit_register'] ) {
 echo "<script src='js/register.js'></script>";
}

but the code above does: the first click import the .js, then at the second click to log in/register, load correctly.

The optimal idea is to load every .js where appropriate. The .js at just one click like all sites.

The code for login.js is:

$(function() {
    $("form").submit(function(e) {
        var datos = $("form").serialize();
        $.ajax({
            method: "POST",
            url: "loginCode.php?type=pdo",
            data: datos,
            success: function(data) {
                switch($.trim(data)) {
                    case "success":
                            notification("success", "Usuario válido");
                         $(location).attr('href','index.php');
                        break;
                    case "failed":
                            notification("failed", "Usuario no válido");
                        break;
                    default:
                }
            }
        })
        e.preventDefault();
    });

});
function notification(type, text) {
    $notify = $("<div class='notification " + type + "'></div>").appendTo("#notification_wrapper");
    $notify.append("<div class='errorImage'></div><div class='info'>" + text + "</div>");
    $notify.fadeIn().delay(3000).fadeOut('fast');
}

And the code for register.js:

$(function() {
    $("form").submit(function(e) {
        var datos = $("form").serialize();
        $.ajax({
            method: "POST",
            url: "signupCode.php?type=pdo",
            data: datos,
            success: function(data) {
                switch($.trim(data)) {
                    case "success1":
                            notification("success", "Registro completado");
                        break;
                    case "failed1":
                            notification("failed", "Ha ocurrido un error");
                        break;
                    default:
                }
            }
        })
        e.preventDefault();
    });

});
function notification(type, text) {
    $notify = $("<div class='notification " + type + "'></div>").appendTo("#notification_wrapper");
    $notify.append("<div class='errorImage'></div><div class='info'>" + text + "</div>");
    $notify.fadeIn().delay(3000).fadeOut('fast');
}

The html form login is quite normal like this:

<form id="form_1" action="" method="post">
    <input type="submit" name="submit_login" value="Submit" />
</form>

<form id="form_2" action="" method="post">
    <input type="submit" name="submit_register" value="Submit" />
</form>

Hope u can help me, I was trying to do that 1 week ago but this wins me. Sorry if my english is not so good. Thanks u in advance.