Prototype - Object isUndefined() Method

Quiz

This method returns true if obj is of type undefined, false otherwise.

Syntax

Object.isUndefined(obj);

Return Value

Returns true if obj is of type undefined, false otherwise.

Example

<html>
   <head>
      <title>Prototype examples</title>
      <script type = "text/javascript" src = "/javascript/prototype.js"></script>
      
      <script>
         function showResult() {
            alert( "test 1: " + Object.isUndefined() );
            alert( "test 2: " + Object.isUndefined(undefined) );
            alert( "test 3: " + Object.isUndefined(null) );
            alert( "test 4: " + Object.isUndefined(0) );
         }
      </script>
   </head>

   <body>
      <p>Click the button to see the result.</p>
      <br />
      <br />
      <input type = "button" value = "Result" onclick = "showResult();"/>
   </body>
</html>

Output

prototype_basic_object.htm

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