Function javascript qui ne marche pas

    <body>

<p id="entete">YUTO ART</p> <br></br>
<br></br>
<br></br>


 <form action="redirection (2).php" id="formulaire" name="formulaire" onsubmit="return 
 validation(this.form)" method="post"    >

<div class="formulaire">

<input type="text " name="prenom"  placeholder="votre prenom" class="champ"
 id="prenom" required :focus ><br></br><br></br>
 
 <input type="text " name="nom"  placeholder="votre prenom" class="champ"
 id="nom" required :focus ><br></br><br></br>

 <input type="text " name="nomutilisateur"  placeholder="votre nom utilisateur" class="champ"
 id="nomutilisateur" required :focus ><br></br><br></br>

 <input type="email " name="email"  placeholder="votre email" class="champ"
 id="email" required :focus ><br></br><br></br>
 
 <input type="date" name="userdate"  placeholder="votre date de naissance" class="champ"
 id="userdate" required :focus ><br></br><br></br>

 <textarea id="userdescription" rows="3" aria-placeholder="description"></textarea>


<center><button class="btn"><input type="submit" name="submit" id="submit" value="ENREGISTRER"  onclick=""></button></center>

</div>





</form>

var lastnameUser=document.getElementById('prenom');
var nameUser=document.getElementById('nom');
alert('bonjour');
document.getElementById('btnn').addEventListener('click',function(t){
    e.preventDefault();
   alert('redirection');

   return false;
});