i am new at programming and my I think my question is easy, but I don't have any ideas. How to check if the number of characters in a text field matches 11? I tried this but I don't think that's a good lead.

<form name="formz">
         <input type='text' name='numbere' id="p"  maxlength="11">  
</form> 

<button onclick="writee()">x</button>
        <script>
function writee(){


    win=window.open(" ","tab","width=300,height=350")
      win.document.open()



 var l = document.forms["formz"].numbere;
 if(l.length==11){
    win.document.write( "under 11 characters <br/>");
 }else{
    win.document.write( " 11 characters <br/>");
 }
}