IntelliJ IDEA 2017.3 Help

Compiling CoffeeScript to JavaScript

This feature is supported in the Ultimate edition only.

On this page:

Introduction

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 compilation and the tools that perform it are called compilers.

IntelliJ IDEA supports integration with the coffee-script compiler. 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. To use the compiler in IntelliJ IDEA, you need to configure it as a File Watcher. For each supported compiler, IntelliJ IDEA provides a predefined File Watcher template. To run a compiler in your project, create a project-specific File Watcher based on the relevant template.

The easiest way to install the CoffeeScript compiler is to use the Node Package Manager (npm), which is a part of Node.js. See NPM for details.

Depending on the desired location of the CoffeeScript compiler executable file, choose one of the following methods:

  • Install the compiler globally at the IntelliJ IDEA level so it can be used in any IntelliJ IDEA project.
  • Install the compiler in a specific project and thus restrict its use to this project.
  • Install the compiler in a project as a development dependency.

In either installation mode, make sure that the parent folder of the CoffeeScript compiler is added to the PATH variable. This enables you to launch the compiler from any folder.

IntelliJ IDEA provides user interface both for global and project installation as well as supports installation through the command line.

Before you start

  1. Download and install Node.js. The runtime environment is required for two reasons:
    • The CoffeeScript compiler is started through Node.js.
    • NPM, which is a part of the runtime environment, is also the easiest way to download the CoffeeScript compiler.

    If you are going to use the command line mode, make sure the path to the parent folder of the Node.js executable file and the path to the npm folder are added to the PATH variable. This enables you to launch the CoffeeScript compiler and npm from any folder.

  2. Install and enable the NodeJS repository plugin as described in Installing, Updating and Uninstalling Repository Plugins and Enabling and Disabling Plugins.
  3. Install and enable the File Watchers repository plugin.

    The plugin is not bundled with IntelliJ IDEA, but it is available from the IntelliJ IDEA plugin repository plugin repository. See Installing, Updating and Uninstalling Repository Plugins and Enabling and Disabling Plugins for details.

Installing the CoffeeScript compiler globally

Global installation makes a compiler available at the IntelliJ IDEA level so it can be used in any IntelliJ IDEA project. Moreover, during installation the parent folder of the compiler is automatically added to the PATH variable, which enables you to launch the compiler from any folder.

  • Run the installation from the command line in the global mode:
    1. Open the embedded Terminal (View | Tool Windows | Terminal) and switch to the directory where NPM is stored or define a PATH variable for it so it is available from any folder, see Installing NodeJs.
    2. Type the following command at the command prompt:
      npm install -g coffee-script

      The -g key makes the compiler run in the global mode. Because the installation is performed through NPM, the CoffeeScript compiler is installed in the npm folder. Make sure this parent folder is added to the PATH variable. This enables you to launch the compiler from any folder.

      For more details on the NPM operation modes, see npm documentation. For more information about installing the CoffeeScript compiler, see https://npmjs.org/package/coffee-script.

  • Run NPM from IntelliJ IDEA using the Node.js and NPM page of the Settings dialog box.
    1. Open the Settings / Preferences Dialog by pressing Ctrl+Alt+S or by choosing File | Settings for Windows and Linux or IntelliJ IDEA | Preferences for macOS, and click Node.js and NPM under Languages & Frameworks.
    2. On the Node.js and NPM page that opens, the Packages area shows all the Node.js-dependent packages that are currently installed on your computer, both at the global and at the project level. Click /help/img/idea/2017.3/new.png.
    3. In the Available Packages dialog box that opens, select the required package to install.
    4. Select the Options checkbox and type -g in the text box next to it.
    5. Optionally specify the product version and click Install Package to start installation.

Installing the CoffeeScript compiler in a project

Local installation in a specific project restricts the use of a compiler to this project.

  • Run the installation from the command line:
    1. Open the embedded Terminal (View | Tool Windows | Terminal) and switch to the project root folder.
    2. At the command prompt, type npm install coffee-script.
  • Run NPM from IntelliJ IDEA using the Node.js and NPM page of the Settings dialog box.
    1. Open the Settings / Preferences Dialog by pressing Ctrl+Alt+S or by choosing File | Settings for Windows and Linux or IntelliJ IDEA | Preferences for macOS, and click Node.js and NPM under Languages & Frameworks.
    2. On the Node.js and NPM page that opens, the Packages area shows all the Node.js-dependent packages that are currently installed on your computer, both at the global and at the project level. Click /help/img/idea/2017.3/new.png.
    3. In the Available Packages dialog box that opens, select the required package.
    4. Optionally specify the product version and click Install Package to start installation.

Project level installation is helpful and reliable in template-based projects of the type Node Boilerplate or Node.js Express, which already have the node_modules folder. The latter is important because NPM installs the CoffeeScript compiler in a node_modules folder. If your project already contains such folder, the CoffeeScript compiler is installed there.

Projects of other types or empty projects may not have a node_modules folder. In this case npm goes upwards in the folder tree and installs the CoffeeScript compiler in the first detected node_modules folder. Keep in mind that this detected node_modules folder may be outside your current project root.

Finally, if no node_modules folder is detected in the folder tree either, the folder is created right under the current project root and the CoffeeScript compiler is installed there.

In either case, make sure that the parent folder of the CoffeeScript compiler is added to the PATH variable. This enables you to launch the compiler from any folder.

Creating a File Watcher

IntelliJ IDEA 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 Settings/Preferences dialog box by choosing File | Settings for Windows and Linux or IntelliJ IDEA | Preferences for macOS on the main menu, and then click File Watchers under the Tools node. 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+Insert and choose the CoffeeScript predefined template from the pop-up list. Your code will be translated to JavaScript and supplied with generated source maps.
  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.

Examples of customizing the behaviour of a compiler

Any compiler is an external, third-party tool. Therefore the only way to influence a compiler is pass arguments to it just as if you were working in the command line mode. Below are two examples of customizing the default output location for the CoffeeScript compiler.

Suppose, you have a project with the following folder structure:

/help/img/idea/2017.3/fileWatcherExampleImage1.png
By default, the generated files will be stored in the folder where the original file is. You can change this default location and have the generated files stored in the js folder. Moreover, you can have them stored in a flat list or arranged in the folder structure that repeats the original structure under the app node.

  • To have all the generated files stored in the output js folder without retaining the original folder structure under the app folder:
    1. In the Arguments text box, type:
      --output $ProjectFileDir$\js\ --compile --map $FileName$
    2. In the Output paths to refresh text box, type:
      $ProjectFileDir$\js\$FileNameWithoutExtension$.js:$ProjectFileDir$\js\$FileNameWithoutExtension$.map

    As a result, the project tree looks as follows:

    /help/img/idea/2017.3/fileWatcherExampleImage2.png

  • To have the original folder structure under the app node retained in the output js folder:
    1. In the Arguments text box, type:
      --output $ProjectFileDir$\js\$FileDirRelativeToProjectRoot$\ --compile --map $FileName$
    2. In the Output paths to refresh text box, type:
      $ProjectFileDir$\js\$FileDirRelativeToProjectRoot$\$FileNameWithoutExtension$.js:$ProjectFileDir$\js\$FileDirRelativeToProjectRoot$\$FileNameWithoutExtension$.map

    As a result, the project tree looks as follows:

    /help/img/idea/2017.3/fileWatcherExampleImage3.png

Compiling the CoffeeScript code

When you open a CoffeeScript file, IntelliJ IDEA checks whether an applicable file watcher is available in the current project. If such file watcher is configured but disabled, IntelliJ IDEA 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, IntelliJ IDEA starts it automatically upon the event specified in the New Watcher dialog.

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

The compiler stores the generated output in a separate file. The file has the name of the source CoffeeScript file and the extension js or js.map depending on the compiler 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, IntelliJ IDEA detects the compiler output. However, in the Project Tree, they are shown under the source .coffee file which is now displayed as a node.

Previewing the compilation results without running a compiler

IntelliJ IDEA can perform static analyses of your CoffeeScript code without actually running a compiler and display the predicted compilation 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 compiler when it runs.
Last modified: 11 October 2017

See Also

Language and Framework-Specific Guidelines: