Prototype Form.Element clear() Method

Syntax:

formElement.clear();

Return Value :

It returns an HTMLElement.

Example:

This code sets up a text field in a way that it clears its contents the first time it receives focus:

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

function showResult()
{
   $('username').onfocus = function() {
     // if already cleared, do nothing
     if (this._cleared) return
	 
	 // otherwise clear this
	 this.clear()
     this._cleared = true
   }
}

</script>
</head>

<body onload="showResult();">

  <p>Focus on username to see the result:</p>
  <br />

  <form id="example" action="#" onsubmit="return false">
  <fieldset><legend>User info</legend>
  <div><label for="username">Username:</label> 
  <input name="username" id="username" value="Sai" type="text">
  </div>
  <div><label for="age">Age:</label> 
  <input name="age" id="age" value="23" size="3" type="text">
  </div>

  <div><label for="hobbies">Your hobbies :</label>
  <select name="hobbies" id="hobbies" multiple="multiple">
    <option>coding</option>
    <option>swimming</option>
    <option>hiking</option>
    <option>drawing</option>
  </select></div>
  </fieldset>
  </form>

</body>
</html>

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