From JQuery $() function to JavaScript getElementByID

I have a snippet of code that keeps putting out an error message. The problem is that the snippet is in JQuery and I do not know that language.

I am told that the problem is with the JQuery's implementation of the $() function, (which is supposed to serve as a universal way to implement a "superset" of the getElementById() function).

I'm not sure how to begin, but the JQuery snippet needs to be recoded into JavaScript using traditional coding like getElementById.

Any suggestions?

Code:

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57              $(document).ready(function() {
58
59                  $(".signin").click(function(e) {         
60                      e.preventDefault();
61                      $("fieldset#signin_menu").toggle();
62                      $(".signin").toggleClass("menu-open");
63                      document.forms["loginForm"].elements.loginUser.focus();
64                  });
65
66            $("fieldset#signin_menu").mouseup(function() {
67                      return false
68                  });
69                  $(document).mouseup(function(e) {
70                      if($(e.target).parent("a.signin").length==0) {
71                          $(".signin").removeClass("menu-open");
72*                        $("fieldset#signin_menu").hide();
73                      }
74                  });       
75
76              });

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Thanks.