12.6 JavaScript Debugger

Dreamweaver 4 includes a JavaScript debugger that allows you to debug JS code, but there are some caveats.

The debugger:

  • Requires NN4.5+ (Macintosh and Windows, but excluding NN6) or IE4+ (Windows only).

  • Requires that both Java and JavaScript be enabled in your browser's preferences.

  • Will debug JS code embedded in HTML documents or stored in external .js files.

  • Will not work in any version of IE on the Mac, in any version of NN6 on either platform, or in Opera.

  • Will not debug JS code when you use frames . You must debug each framed HTML page separately.

  • Will not debug JS code in templates or documents attached to templates. You must detach a document from its template before debugging it.

  • May not work on the Macintosh if TCP/IP access is set to AppleTalk or PPP. The workaround, as described in Macromedia TechNote 15020, is to change the TCP/IP setting to connect via a different method.

  • May hinder system performance or interfere with other operations such as viewing the Help files in the browser. Close the debugger when it is no longer needed.

12.6.1 Running the Debugger

To run the debugger you must brave a slew of dialog boxes:

  1. Open the HTML document you want to debug (you can't start the debugger while editing as .js file). Save any recent changes to the file.

  2. With your HTML document open, select File figs/u2192.gif Debug in Browser figs/u2192.gif browser .

  3. Dreamweaver checks your code for syntax errors and reports errors in the JavaScript Syntax Errors dialog box shown in Figure 12-7.

  4. If there are no syntax errors, Dreamweaver launches the debugger for the chosen browser. If asked whether to start debugging, click OK.

  5. Because the debugger itself is a Java applet, the browser displays an ominous warning about potential security risks of network access (the debugger connects with the browser but does not make any network connections).

  6. If using Internet Explorer, Click the Yes button in Internet Explorer's Security Warning dialog box (not shown). You can accept the Macromedia Security Certificate by clicking the Macromedia Dreamweaver name in this dialog box and then clicking the Install Certificate option. If asked whether to start debugging, click OK.

  7. If using Netscape, click the Grant button in Netscape's Java Security dialog box (not shown). Click the Remember This Decision checkbox in that dialog box to avoid being asked again next time.

  8. Finally, the JavaScript Debugger opens (see Figure 12-8).

Let's looks a little more carefully at some of the debugging tools. The JavaScript Syntax Errors dialog box

The JavaScript Syntax Errors dialog box, shown in Figure 12-7, provides the filename, line number, error type, and description for each error. When you select an error from the list, the bottom of the dialog provides a detailed description of the usual cause of such errors. Use the Go To Line button (or simply double-click one of the errors in the list) to find the corresponding line in the script where you should fix the error.

Figure 12-7. The JavaScript Syntax Errors dialog box
figs/dwn_1207.gif The JavaScript Debugger window

Dreamweaver's debugger offers the typical features needed to find and fix errors, such as the ability to set breakpoints, watch variables , and step through your code. See "Debugging JavaScript Code" in the online Help for a quick overview, especially if you've never use a debugger before. The JavaScript Debugger is shown in Figure 12-8. The lower pane (the Watcher) is used to examine variables and change their values.

Figure 12-8. The JavaScript Debugger

Here are some quick hints regarding the debugger:

  • Before starting a debugging session, you can set breakpoints in your embedded scripts (those within your HTML file) or in external scripts (those in .js files). You'll be warned if you haven't set at least one breakpoint before running the debugger.

  • Use the Run button in the debugger's toolbar to begin execution or to continue execution until the next breakpoint is reached.

  • You'll often need to interact with the browser to trigger a script. For example, if testing a rollover effect, you should roll the mouse over the button of interest in the browser. Be sure to place breakpoints where they'll actually be reached (setting a breakpoint in a function that is never called won't help). When a breakpoint is reached, the Debugger window should come to the front.

  • The debugger may hinder system performance and prevent you from viewing the online Help. Stop the debugger when it is no longer needed.

  • If your browser doesn't respond, the debugger may be paused . Use the Run button (F8) to resume execution. If nothing seems to work, try quitting your browser and restarting the debugger.

  • Type javascript: on the Netscape browser's command line to open its JavaScript console where you can see error messages or test JS code. This console helps to solve problems not apparent in Dreamweaver's debugger, such as when the browser can't find a particular function in your JS code.

Table 12-6 summarizes the debugging operations. To set a breakpoint, click the line in your script at which to add the breakpoint, and then click the Add/Remove Breakpoint icon.

In Code view, you can use the Code Navigation menu (see Figure 12-6) to set breakpoints in a JS function or on the line containing the HTML tag that calls the function. In the latter case, once the breakpoint is reached, click the Step Into icon to debug your JS function (you may need to click it more than once). Breakpoints can also be set in the debugger itself.

To monitor a variable's value, highlight its name in the debugger window and click the plus (+) button (see Figure 12-8). This adds the variable to the watch list. You can also click the plus (+) button and type in the name of a variable. You can change a variable's value in the Value column of the watcher pane.

Table 12-6. Debugger command summary


Menu option or icon



Debug in primary browser

File figs/u2192.gif Debug in Browser figs/u2192.gif browser1



Debug in secondary browser

File figs/u2192.gif Debug in Browser figs/u2192.gif browser2



Run (continue to next breakpoint)

Run icon



Close debugger

Stop Debugging icon


Close box

Add/Remove breakpoint

Edit figs/u2192.gif Set/Remove Breakpoint or icon

F7 or Ctrl+Alt+B

F7 or Cmd+Opt+B

Clear all breakpoints

Edit figs/u2192.gif Remove All Breakpoints or icon

Alt+E, V


Step over a function

Step Over icon



Step into a function

Step Into icon



Step out of a function

Step Out icon



Watch variable

Plus (+) button in lower pane



Remove watched variable

Minus (-) button in lower pane



Dreamweaver in a Nutshell
Dreamweaver in a Nutshell
Year: 2005
Pages: 208

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