o    So far, we have seen brief examples of alert, prompt and confirm dialogue boxes to request a response from the user, and to pause all code in the background until the request is satisfied.

o    All of these boxes are the result of methods of the window object. This object is the highest level object that JavaScript can deal with in a browser. As such, all other objects on a page (with a few exceptions) are actually properties of the window object.

o     Because of this ubiquity, its presence is assumed even if it is omitted. Thus, where we technically should write:

 window.document.write(“…”);

 it is equally valid to write:

 document.write(“…”);

 as we have been doing.

o     Similarly, instead of writing:

 window.alert(“…”);

we can happily write:

 alert(“…”);

o    The prototypes of the three methods are:

        window.alert( message ); window.confirm( message ); window.prompt( message, default_response );

o    Alert will always return a value of “true” when it is cleared by clicking “ok”.

o    Confirm will return either “true” or “false” depending on the response chosen to clear the box.

o    Prompt will return either the value typed in, “null” if nothing is typed in, and “false” if the box is cancelled.

Project

o   Open your previous project file, and save it under the name chapter_10.html.

o   Clear the previous redirection code, and ensure that the script tags have been returned to the head section of the document.

o   Add a new statement to the script on the page that will display the following message before the rest of the page is shown:

 Welcome to my website! Click OK to continue.

o Check your page in your browser.

 o   We will use alert, confirm, and prompt throughout this course. Take a moment to try each of them in turn on this page, each time stopping to review your changes.

 o   Use the write method of the document object to check the return values of each method. For example:

          document.write(alert(“hello world”));