2.1 Game 2302-0310 javascript  (Page 2/11)

Facilities required

To use JavaScript for its intended purpose in the modules in this collection, you will need the following:

• Access to the Internet.
• A modern browser such as Firefox 3.6 (see (External Link) ).
• A plain text editor such as Windows notepad, or my favorite, Arachnophilia, which can be downloaded for free at (External Link) .

A minimal JavaScript script

Listing 1 shows a minimal JavaScript script.

Run the script

To run this JavaScript script:

• Copy all of the text from the body of Listing 1 into your plain text editor and save the file with an extension of .html (test.html forexample).
• Open that file in your browser. (In most cases, you should be able to simply drag the file and drop it onto an open browser page to open it. Ifthat doesn't work, open it from the browser's File menu.)

And the result is...

When you do that, the text shown in Figure 1 should appear in the browser window.

That's all there is to it

All you have to do to write and run a JavaScript script is to:

• Copy the text (often referred to as code or source code) from Listing 1 into your plain text editor.
• Replace the code between the two lines containing the word script with the code for your new script, leaving the two lines containing the word script intact.
• Save the file with an extension of .html. (The file can have any legal file name so long as the extension is .html.)
• Open the new html file in your browser.

When you do that, the script code will be executed.

Display results in the browser window

If your script code contains statements that begin with document.write , followed by a pair of matching parentheses, (as shown in Listing 1 ), the code in the parentheses will be evaluated and the results of that evaluation will appear in your browser window.

At that point, you will have access to your script code as well as the results of running your script.

Strings

In programming, we often refer to a group of sequential characters (such as your first name) as a string . In JavaScript format (often called syntax), such groups of characters are surrounded by matching quotationmarks to cause the group to be recognized as a single string.

The following strings appear in the JavaScript code in Listing 1 :

1. "Insert JavaScript between script tags."
2. "<br/>"
3. "Hello from JavaScript"

The first two strings appear, separated by a comma, inside the matching parentheses following the first occurrence of document.write . (We often call the items inside the matching parentheses the argument list.)

The last item in the above list appears in the argument list following the second occurrence of document.write in Listing 1 .

Screen output

If you examine Figure 1 , you will see that the first and third items from the above list appear, without their quotation marks, in the browser window. However, the second item does not appear in the browser window.