<html>

<head> <title> JavaScript example </title>

</head>

 

<body onLoad="window.alert('I sure hope you bookmarked this website!')"

      bgcolor="#FFFFFF" text="#000000">

 

     <h1>  This is an example with JavaScript </h1>

 

</body>

</html>

 

 

 

Result

 

 

A few comments:

  1. OnLoad is a called an event handler. OnLoad tells the browser that the event must happen when the web page is first or initially loaded (that is, produce this Alert window onLoading the web page).
  2. When the browser sees window.alert(), it knows what to do. Window is called an object and alert() is called a method of the window object. An object can have many methods and for the window object, alert( ) is one them.
  3. The message is called an argument and arguments must always be enclosed within parentheses. The argument belongs to the method alert( ) and note that it is enclosed with single quotation marks. Note that the whole statement for the onLoad event handler is enclosed with double quotation marks. When two sets of quotation marks are required, then one set must be double and the other set must be single quotation marks. Otherwise the browser will be unable to keep things straight. Omitting these quotation marks will result in an error message. Note that these quotation marks did not appear in the pop-up window.
  4. If you want the message to be displayed only when the visitor leaves your web page, use onUnload instead of onLoad. You can also change the message to suit your own needs.

Note: The onLoad attribute of the BODY tag (onLoad="window.alert('I sure hope you bookmarked this website!')") must be printed on one line in Notepad or in whatever text editor you are using. A browser looks for the closing quotation marks on the same line as the opening quotation marks. If the closing quotation marks are on a different line, you have a JavaScript error and the script will not work. Therefore make sure that onLoad="window.alert('I sure hope you bookmarked this website!')" appears all on the same line in your text editor such as Notepad.

Also note that the JavaScript Alert window that appeared when you loaded this web page will appear every time you re-load or return to this page.