javascript - Why when trying to use JQuery on a previously initialized html element variable it returns undefined? -


i read on jquery docs ( https://learn.jquery.com/using-jquery-core/faq/how-do-i-select-elements-when-i-already-have-a-dom-element/ ) use initialized element writing variable name selectors:

$(element)

but whenever try function call @ press of button returns 'undefined'.

this example code did test out in more controlled environment: 

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>  <div class="container-fluid">      <div class="row">          <div class="col-md-6">              <button class="btn btn-block btn-primary" onclick="jquery(this)">jquery</button>          </div>          <div class="col-md-6">              <button class="btn btn-block btn-info" onclick="normaljs(this)">normaljs</button>          </div>      </div>      <div class="row">          <div class="col-md-6">              <button class="btn btn-block btn-danger" onclick="basictest()">basictest</button>          </div>          <div class="col-md-6">              <button class="btn btn-block btn-info" id="empty">dynamictest</button>          </div>      </div>  </div>  <script>      function jquery(caller){          var element = $(caller).parent();          alert("tag name: " + element.tagname);      }        function normaljs(caller){          var element = caller.parentelement;          alert("tag name: "+ element.tagname);      }        function basictest(){          alert("this basic test");      }        $("#empty").click(function(){          alert("tag name: " + $(this).tagname);          alert("tag name: " + this.tagname);      });  </script>

am doing wrong?

by $(caller), "converted" dom element jquery object, therefore, dom properties , methods won't work in normal way on anymore, if want tagname using jquery, prop() :

function jquery(caller){     var element = $(caller).parent();     alert("tag name: " + element.prop("tagname")); }

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