PyCharm 3.1.0 Web Help

Some features described here are available in Professional edition only.

CoffeeScript code is not processed by browsers that work with JavaScript code. Therefore to be executed, CoffeeScript code has to be translated into JavaScript. This operation is referred to as transpilation and the tools that perform it are called transpilers.

PyCharm supports integration with the coffee-script transpilation tool. The tool translates CoffeeScript code into JavaScript and creates source maps that set correspondence between lines in your CoffeeScript code and in the generated JavaScript code, otherwise your breakpoints will not be recognised and processed correctly. So if you want only to run your application, it is enough to apply the coffee-script transpiler while to enable debugging it you will need to run both tools.

In PyCharm, transpiler configurations are called File Watchers. For each supported transpiler, PyCharm provides a predefined File Watcher template. Predefined File Watcher templates are available at the PyCharm level. To run a transpiler against your project files, you need to create a project-specific File Watcher based on the relevant template, at least, specify the path to the transpiler to use on your machine.

On this page:

Installing and configuring a CoffeeScript transpiler
  1. Download and install the Node.js framework. The framework is required for two reasons:
    • The CoffeeScript transpiler is started through Node.js.
    • The Node Package Manager (npm), which is a part of the framework, is also the easiest way to download the transpiler.

    For details on using Node.js in PyCharm, see the section Node.js


    Alternatively, you can define Node.js as an external tool, as described in the section Configuring third-party tools. This approach is helpful, when you need facilities that are missing in the plugin, for example, the possibility to pass certain parameters as wildcards.

  2. Make sure the following paths are added to the PATH variable:
    1. The path to the parent folder of the Node.js executable file.
    2. The path to the Node Package Manager folder (npm).
    This enables you to launch the CoffeeScript transpiler and the Node Package Manager (npm) from any folder.
  3. Install and enable the NodeJS repository plugin.

    The plugin is not bundled with PyCharm, but it is available from the PyCharm plugin repository. Once enabled, the plugin is available at the IDE level, that is, you can use it in all your PyCharm projects.

  4. Make sure the File Watchers plugin is enabled. The plugin is bundled with PyCharm and activated by default. If it is not, enable the plugin.
  5. Download and install the CoffeeScript transpiler. The easiest way is to use the Node Package Manager (npm), which is a part of Node.js.
    1. Switch to the directory where the Node Package Manager (npm) is stored or define a path variable for its parent folder so it is available from any folder.
    2. To run and debug the generated JavaScript code, download the coffee-script through the following command at the command line prompt:
      npm install coffee-script

      To debug your code, you will need source maps that set correspondence between lines in your CoffeeScript code and the generated JavaScript code, otherwise your breakpoints will not be recognised and processed correctly. Source maps are also generated by the coffee-script tool.

      The tool is installed under Node.js so Node.js, which is required for starting the tool, will be specified in the path to it.


      The executable files of the transpiler have the name coffee.cmd.

      For more information about installing the CoffeeScript transpiler, see

Creating a File Watcher

PyCharm provides a common procedure and user interface for creating File Watchers of all types. The only difference is in the predefined templates you choose in each case.

  1. To start creating a File Watcher, open the Project Settings and click File Watchers. The File Watchers page that opens, shows the list of File Watchers that are already configured in the project.
  2. Click the Add button new.png or press Alt+InsertAlt+InsertAlt+InsertAlt+InsertAlt+InsertAlt+InsertAlt+Insert or Ctrl+NAlt+InsertCommand N or Control EnterControl N or Control EnterCommand N or Control Enter and choose the predefined template from the pop-up list.
    • If you are going to run your CoffeeScript without debugging, choose CoffeeScript. Your code will be just translated to JavaScript.
    • If you are going to debug your code, choose CoffeeScript Source Map. As a result, the source maps will be created.
  3. In the Program text box, specify the path to the coffee.cmd file. Type the path manually or click the Browse button browseButton.png and choose the file location in the dialog box that opens.
  4. Proceed as described on page Using File Watchers: .

Transpiling the CoffeeScript code

When you open a CoffeeScript file, PyCharm checks whether an applicable file watcher is available in the current project. If such file watcher is configured but disabled, PyCharm displays a pop-up window that informs you about the configured file watcher and suggests to enable it.

If an applicable file watcher is configured and enabled in the current project, PyCharm starts it automatically upon the event specified in the New Watcher dialog.

  • If the Immediate file synchronization check box is selected, the File Watcher is invoked as soon as any changes are made to the source code.
  • If the Immediate file synchronization check box is cleared, the File Watcher is started upon save (File | Save All, Ctrl+SCtrl+SCtrl+SCtrl+SCtrl+X, Ctrl+SCtrl+SCtrl+S or Ctrl+Shift+SCtrl+SCommand SCommand SCommand S) or when you move focus from PyCharm (upon frame deactivation).

The transpiler stores the generated output in a separate file. The file has the name of the source CoffeeScript file and the extension js or depending on the transpiler type. The location of the generated files is defined in the Output paths to refresh text box of the New Watcher dialog. Based on this setting, PyCharm detects transpiler output. However, in the Project Tree, they are shown under the source .coffee file which is now displayed as a node.

Previewing the transpilation results without running a transpiler

PyCharm can perform static analyses of your CoffeeScript code without actually running a transpiler and display the predicted transpilation output in the dedicated read-only viewer.

  1. Open the desired CoffeeScript file in the editor, and right-click the editor background.
  2. On the context menu, choose Preview Compiled CoffeeScript File. The preview is opened in the dedicated read-only viewer: the left-hand pane shows the original CoffeeScript source code and the right-hand pane shows the JavaScript code that will be generated by the transpiler when it runs.

See Also


Language and Framework-Specific Guidelines:


External Links:

Web Resources: