Chapter 2: How to code a JavaScript application

This chapter presents a subset of JavaScript and DOM scripting that will soon have you writing significant applications. If you don't have any programming experience, this chapter also makes a great aptitude test. If you read it and can do the exercises at the end of the chapter, you're ready for the rest of this book.

How to edit and test your web pages

Before you can create a JavaScript application, you need to know how to edit and test a web page. To get you started, this topic provides the basic skills that you'll need. Then, in chapter 3, you'll learn more about testing and debugging.

How to edit a web page with Notepad++

Although you can use any text editor to enter and edit XHTML, CSS, and JavaScript files, using a better editor can speed development time and help reduce coding errors. Some features to look for in a text editor are syntax highlighting, auto-completion, and FTP access.

If you're using Windows, we recommend that you use Notepad++ as your editor because it provides all of these features. In addition to Notepad++, though, there are many other free and commercial text editors. For instance, Adobe Dreamweaver and Microsoft Expression Web Designer are two popular commercial editors. For the purposes of this book, however, Notepad++ provides all of the features that you'll need.

If you're a Mac OS user, we recommend that you use TextWrangler as your editor. This is a free editor that provides syntax highlighting and FTP access, although it doesn't provide auto-completion. Here again, though, you have other choices like commercial editors that do provide auto-completion. Three that do are BBEdit (the commercial version of TextWrangler), TextMate, and Dreamweaver.

To illustrate the use of a text editor for web pages, figure 2-1 shows Notepad++ as it's being used to edit a JavaScript file. As you can see, this editor provides tabs so you can edit more than one file at the same time. It color codes the syntax of the statements to reflect different coding elements. And its autocompletion feature helps you complete HTML, CSS, or JavaScript entries. If you experiment with Notepad++, you'll find that it has many other capabilities that this brief summary doesn't present.

Before you start using Notepad++, you should take the time to turn on the auto-completion feature. You will also want to change the style for comments because the default style is too small. These skills are summarized in this figure.

Then, when you start a new file, you should let Notepad++ know what language you're working with. To do that, you can either save the file with the .html, .css, or .js extension, or you can use the Language menu to select the language. Once you do that, this editor uses the appropriate color coding and auto-completion lists.

One feature not shown in this figure is how to access the files on an FTP server with Notepad++. To find out how to do that, you can search the Internet for "Notepad++ FTP".

Notepad++ with six tabs open and an auto-completion list displayed

How to open, save, close, and start files

• To open a file, use the FileOpen command. Or, right-click on the file in the Windows Explorer and select the Edit with Notepad++ command. The file is opened in a new tab.
• To save or close a file, select the tab that it's in and use the FileSave or FileClose command. Or right-click on the tab, and select the appropriate command.
• To start a new file in a new tab, use the FileNew command.

How to change the style for comments

• Start the SettingsStyler Configurator command, and select JavaScript in the language list and COMMENT in the style list. Then, change the font name and font size in the drop-down lists to the blank entries at the top of the lists.
• Repeat this for COMMENTLINE and COMMENTDOC for the JavaScript language, for COMMENT for the HTML language, and for COMMENT for the CSS language.

How to use the auto-completion feature

• To enable auto completion, use the SettingsPreferences command, click the Backup/Auto-completion tab, and check the "Enable Auto-completion on each input" box.
• The auto-completion feature displays a list of terms that start with what you've typed. To insert one of those terms, double-click on it or use the arrows keys to highlight it and press the Tab key. To show the auto-completion list at any time, press Ctrl+Space.

How to let Notepad++ know which language you're working with

• Notepad++ provides color coding for each of the languages that you'll be using: HTML, CSS, and JavaScript. For a new file, you can use the Language menu to select the language that you're using. Or, you can save the file with the appropriate extension.

Figure 2-1 How to edit a web page with Notepad++