Prototype - Periodical Execution


Advertisements


Many times it is required to execute a function many times after a certain period of time. For example, you may want to refresh your screen after a given time. Prototype provides a simple mechanism to implement it using PeriodicalExecuter object.

The advantage provided by PeriodicalExecuter is that it shields you against multiple parallel executions of the callback function.

Creating a PeriodicalExecuter

The constructor takes two arguments −

  • The callback function.
  • The interval (in seconds) between executions.

Once launched, a PeriodicalExecuter triggers indefinitely, until the page unloads or the executer is stopped using stop() method.

Example

Following is the example which will pop up a dialogue box after every 5 seconds untill you will stop it by pressing "cancel' button.

<html>
   <head>
      <title>Prototype examples</title>
      <script type = "text/javascript" src = "/javascript/prototype.js"></script>
      
      <script>
         function startExec() {
            new PeriodicalExecuter(function(pe) {
               if (!confirm('Want me to annoy you again later?'))
               pe.stop();
            }, 5);
         }
      </script>
   </head>

   <body>
      <p>Click start button to start periodic executer:</p>
      <br />
      <br />
      <input type = "button" value = "start" onclick = "startExec();"/>
   </body>
</html>

Output



Advertisements