CLion 2019.3 Help

Running and Debugging Node.js

CLion helps you run and debug your Node.js applications. You can debug applications that are started from CLion as well as attach to already running applications.

Before you start

Install and enable the NodeJS plugin on the Plugins page as described in Installing plugins from repository.

Debugging a Node.js application

CLion makes it easier to debug Node.js applications. You can put breakpoints right in your JavaScript or TypeScript code so you no longer need any debugger and console.log() statements. You can do many things that will help you explore the code and understand where the bug is. In the Debug tool window, you can view the call stack and the variables in their current state, evaluate expressions in the editor, and step through the code.

You can initiate a debugging session in two ways:

  • Start the debugger together with your application using a Node.js run/debug configuration.

  • Attach the debugger to an already running application. In this case, your application is already running in the debug mode and CLion attaches to a running process.

    CLion recognizes --inspect, --inspect-brk, and now deprecated --debug flags so you can make any application accessible for debugging.

    To debug a running application, use an Attach to Node.js/Chrome configuration.

Starting the debugger together with a Node.js application on your computer

  1. Set the breakpoints in the code where necessary.

  2. Create a Node.js run/debug configuration. If necessary, CLion can generate a JavaScript Debug configuration and start it automatically together with the Node.js configuration.

  3. Select the newly created Node.js configuration from the Select run/debug configuration list on the toolbar and click the Debug button next to it. The Debug Tool Window opens.

  4. Perform the steps that will trigger the execution of the code with the breakpoints.

  5. Switch to CLion, where the controls of the Debug tool window are now enabled. Proceed with the debugging session — step through the breakpoints, switch between frames, change values on-the-fly, examine a suspended program, evaluate expressions, and set watches.

Debugging a Node.js application that uses nodemon

The CLion built-in debugger can automatically reconnect to running Node.js processes. This lets you debug Node.js applications that use the nodemon utility, which automatically reloads your Node.js process when the code is updated.

To debug such application, you need to start it in the debug mode (with the --inspect or --inspect-brk flag) and then connect to it using the Attach to a Node.js/Chrome debug configuration with the Reconnect Automatically option on.

To install nodemon

  • In the embedded Terminal (Alt+F12), type npm install --save-dev nodemon or yarn add nodemon --dev to install nodemon as a development dependency.

To start an application with nodemon in the debug mode

  • Create and run the following npm debug script:

    debug": "nodemon --inspect <path_to_the_file_that_starts_your_application>

    See Running and debugging scripts for details.

To debug an application

  1. Set the breakpoints in your code as necessary.

  2. Create a new Attach to a Node.js/Chrome configuration as described in Debugging a running Node.js application and select the Reconnect automatically checkbox.

    Attach no Node.js run configuration: select the Reconnect automatically checkbox

    Usually, you don’t need to change the port in the configuration 9229 because it’s the default port the debugger is listening on. But you can double-check what port is used in the message logged when you run the app in the debug mode.

    Node.js application with  nodemon running in the debug mode: check the port
  3. Select the newly created Attach to Node.js/Chrome configuration from the Select run/debug configuration list on the toolbar and click Debug button next to it. The debugger stops at the breakpoints that you put in your code in CLion.

    Now, every time you make any changes to the code and save them Ctrl+S, nodemon will automatically reload the application and the debugger will automatically re-attach to the restarted process.

Last modified: 12 December 2019