Regular expression login on jQuery form

Question

I have a problem with a regular expression. console.log shows me the login regular expression isn't respected, but my span doesn't show, my email span works.

I think it's a basic JS/jQuery problem, but I couldn't find the solution.

HTML:

<form name="formSignup">
    <fieldset>

        <label for="nom">Nom :</label>
        <input type="text" name="nom" id="nom" class="required"  />

        <label for="prenom">Prenom :</label>
        <input type="text" name="prenom" id="prenom" class="required"  />

        <label for="email">Votre Email:</label>
        <input type="email" name="email" id="email" class="required" onclick="spanHide()"  />

        <label for="username">Login:</label>
        <input type="text" name="username" id="username" class="required"  />

        <label for="password">Password:</label>
        <input type="password" name="password" id="password" class="required" />

        <input id="Submit1" type="button" value="Login" data-role="button" data-inline="true" data-theme="b" onclick='createuser()' />
    </fieldset>
</form>

JS:

var emailReg = /^([\w-\.]+@([\w-]+\.)+[\w-]{2,4})?$/;
var loginReg= /^[a-zA-Z0-9]+$/;

if (email == '') {
    $("#email").after('<span id="errormail" class="error">Please enter your email address.</span>');
}

if (!loginReg.test(myLogin)) {
    console.log("error");
    $("#username").after('<span id="errorlogin" class="error">only letter + digits plz</span>');
}
if (!emailReg.test(email)) {
    $("#email").after('<span id="errormail" class="error">Enter a valid email address.</span>');
}