Remove outdated visible/hidden detection from jQuery core from Selecting Elements article.

Author: ajpiano

page/using-jquery-core/selecting-elements.md

@@ -57,43 +57,6 @@ However, this test doesn't work with `<tr>` elements. In the case of `<tr>` jQue
 
 Elements that have not been added to the DOM will always be considered hidden, even if the CSS that would affect them would render them visible. See the [Manipulating Elements](/manipulating-elements) section to learn how to create and add elements to the DOM.
 
-For reference, here is the code jQuery uses to determine whether an element is visible or hidden:
-
-```
-jQuery.expr.filters.hidden = function( elem ) {
-
-  var width = elem.offsetWidth;
-  var height = elem.offsetHeight;
-  var skip = elem.nodeName.toLowerCase() === "tr";
-
-  // does the element have 0 height, 0 width,
-  // and it's not a <tr>?
-  return width === 0 && height === 0 && !skip ?
-
-      // then it must be hidden
-      true :
-
-      // but if it has width and height
-      // and it's not a <tr>
-      width > 0 && height > 0 && !skip ?
-
-          // then it must be visible
-          false :
-
-          // if we get here, the element has width
-          // and height, but it's also a <tr>,
-          // so check its display property to
-          // decide whether it's hidden
-          jQuery.curCSS( elem, "display" ) === "none";
-};
-
-jQuery.expr.filters.visible = function( elem ) {
-
-  return !jQuery.expr.filters.hidden( elem );
-
-};
-```
-
 ## Choosing Selectors
 
 Choosing good selectors is one way to improve JavaScript's performance. A little specificity &#8212; for example, including an element type when selecting elements by class name &#8212; can go a long way. On the other hand, too much specificity can be a bad thing. A selector such as `#myTable thead tr th.special` is overkill if a selector such as `#myTable th.special` will get the job done.