Générer un password en Javascript

<script type="text/javascript">

    function generer_password(champ_cible) {
        var ok = 'azertyupqsdfghjkmwxcvbn23456789AZERTYUPQSDFGHJKMWXCVBN';
        var pass = '';
        longueur = 5;
        for(i=0;i<longueur;i++){
            var wpos = Math.round(Math.random()*ok.length);
            pass+=ok.substring(wpos,wpos+1);
        }
        document.getElementById(champ_cible).value = pass;
    }
    /*
       <input name="password" id="password" type="text" />
       <input type="button" name="generer" value="Générer" onclick="javascript:generer_password('password');" />
     */
</script>