https://github.com/joyent/node/wiki/Using-Eclipse-as-Node-Applications-Debugger

Eclipse debugger plugin for V8 can be easily used to debug node scripts. (On OSX 10.5 the plugin requires an Eclipse 64 bit Version, started with Java SE 6). The V8 engine provides debugging support by enabling attachment of the remote debugger on a TCP port (5858 is node’s default). There are 2 debug related node options:

node –debug[=port] NodeApp.js

or

node –debug-brk[=port] NodeApp.js

The –debug option will just enable remote debugger connection on given port and then start the application normally. Even when debugger is connected to the running node instance later on, the script execution will not be stopped until “Suspend” command is issued by Eclipse debugger. Another way to stop the execution is to browse the source code of the JavaScript modules comprising the application and double click on the line number at the desired position in script to break at (most likely a callback). Once execution stops you can set/clear more breakpoints, but also inspect call stack and view content of all program variables.

The –debug-brk option is needed when your script is short lived (no time to attach debugger) and/or you want to observe the NodeApp.js execution from the very start. This option will force execution to break at the first line of the main script and wait for debugger to connect. The behavior upon connection is now different – the script is suspended and no breakpoints are set. Note that V8 engine debugger is not behaving very good when it steps over or steps into require() method (it will crash), so try to set up first breakpoint past the initial module loading. This will also enable you to set breakpoints in any of those modules as well.

Installation

Rather than installing the V8 Eclipse Debugging Plugin on an existing Eclipse Java or Eclipse C++ installation, you might want to install the plugin into its own Eclipse Platform. This prevents an instability of the plugin, Node.js or V8 from disrupting your Java or C++ projects. You can download a clean slate Eclipse Platform, then use the plugin update utility to install V8 Eclipse Debugging Plugin.

• Download a clean slate Eclipse Platform for your operating system.
• Unzip the Eclipse Platform to a directory on your hard drive.
• Run the Eclipse Platform. You will be asked to create a workspace. Create a workspace separate from any Java or C++ workspaces you may already have created. If this is your first time using Eclipse, the default is fine.
• Proceed to the workbench by clicking the icon with the arrow titled Workbench in the top right corner of the Eclipse window.
• Select the menu item Help > Install New Software…. A dialog box titled Install will appear. This contains a plugin installation wizard. The first step of the wizard is titled Available Software.
• At the top of the dialog you will see a combo box labeled Work with:. Click the button to the right of the combo box labeled Add. A dialog box titled Add Repository will appear.
• In the textbox labeled Name: enter Google Chrome Developer Tools. In the textbox labeled Location: enter http://chromedevtools.googlecode.com/svn/update/dev/. Click OK.
• Now select Google Chrome Developer Tools – http://chromedevtools.googlecode.com/svn/update/dev/ from the Work with: combo box. Google Chrome Developer Tools will appear in the table below. Click the checkbox next to Google Chrome Developer Tools in the table. Click the button labeled Next > at the bottom of the dialog box. The next wizard step titled Install Details is displayed.
• Click the button labeled Next >. The next wizard step titled Review Licenses is displayed.
• Once you are satisfied with the licenses, you can select the I accept the terms of the license agreement radio button and click the button labeled Finish. A progress dialog box titled Installing Software will be displayed. After installation is complete click the Restart Now button.
• Eclipse will restart with the V8 Eclipse Debugging Plugin installed.

Sample Debugging Session

Here is a simple script that will be used to demonstrate debugging procedure:

// dbgtest.js

var sys=require(‘sys’);

var count = 0;

sys.debug(“Starting …”);

function timer_tick() {

  count = count+1;

  sys.debug("Tick count: " + count);

  if (count === 10) {

    count += 1000;

    sys.debug("Set break here");

 }

 setTimeout(timer_tick, 1000);

}

timer_tick();

Start the above script:

$ node –debug dbgtest.js

debugger listening on port 5858

DEBUG: Starting ...

DEBUG: Tick count: 1

DEBUG: Tick count: 2

DEBUG: Tick count: 3

// and so on

Assuming that you have already installed Eclipse, together with the plugin mentioned above, now you need to make initial debug profile.

In the Menu, choose Window → Open Perspective → Other, then select Debug from the list and click OK, to ensure you are viewing the debug perspective.