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Prototype descendantOf() Method


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This method checks if element is a descendant of ancestor.

As Element.descendantOf internally applies $() to ancestor, it accepts indifferently an element or an element's id as its second argument.

Syntax:

element.descendantOf(ancestor);

Return Value:

  • If it finds that element is a decendant of an ancestor then it returns true otherwise false

Example:

<html>
<head>
<title>Prototype examples</title>
<script type="text/javascript" 
   src="/javascript/prototype.js">
</script>
<script>


function isDescendant(){
   var father = $('father');
   var kid = $('kid');
   // This is correct relationship and will be printed
   if( kid.descendantOf(father) ){
       alert( "Kid is descendant of father" );
   }
   // This is wrong relationship and will not  be printed
   if( father.descendantOf(kid) ){
       alert( "Father is descendant of kid" );
   }
}

</script>
</head>

<body>

   <p>Click isDescendant button to see the result.</p>
   <div id="grandfather">
      <div id="father">
         <div id="kid"></div>
      </div>
   </div>

   <br />
   <input type="button" value="isDescendant" 
             onclick="isDescendant();"/>

</body>
</html>

To understand it in better way you can Try it yourself.



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