WebStorm 2019.2 Help

CoffeeScript

With WebStorm, you can use CoffeeScript that compiles into JavaScript. WebStorm recognizes *.coffee files and marks them with the CoffeeScript icon. You can set breakpoints directly in your CoffeeScript code and WebStorm recognizes them using source maps generated during compilation.

WebStorm helps you write CoffeeScript code by suggesting completion for keywords, labels, variables, parameters and functions. You can jump from a symbol to its declaration Ctrl+B or implementation Ctrl+Alt+B as well as find any symbol by its name Ctrl+Shift+Alt+N.

Compiling CoffeeScript into JavaScript

WebStorm integrates with the coffee-script compiler that translates CoffeeScript code into JavaScript. The tool also creates source maps that set correspondence between lines in your CoffeeScript code and in the generated JavaScript code so that WebStorm debugger recognizes breakpoints in your CoffeeScript code and processes them correctly. To compile your code on the fly, you need to configure the compiler as a WebStorm File Watcher.

To install the CoffeeScript compiler

In the embedded Terminal (Alt+F12), type one of the following commands:

  • npm install --global coffeescript for global installation.

  • npm install --save-dev coffeescript to install CoffeeScript as a development dependency.

    Learn more from the CoffeeScript Official website.

To create a CoffeeScript File Watcher

  1. In the Settings/Preferences dialog (Ctrl+Alt+S), go to Tools | File Watchers.

  2. Click the Add button or press Alt+Insert and choose the CoffeeScript predefined template from the list. Your code will be translated to JavaScript and supplied with generated source maps.

  3. In the Program field, specify the path to the coffee.cmd file. Type the path manually or click the Browse button and choose the file location in the dialog that opens.

  4. Proceed as described in File Watchers.

Compiling the code

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

  • If the Auto-save edited files to trigger the watcher checkbox is selected, the File Watcher is invoked as soon as any changes are made to the source code.

  • If the Auto-save edited files to trigger the watcher checkbox is cleared, the File Watcher is started upon save (File | Save All, Ctrl+S) or when you move focus from WebStorm (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 field of the New Watcher dialog. Based on this setting, WebStorm detects the compiler output. However, in the Project tool window, they are shown under the source coffee file which is now displayed as a node.

Examples of customizing the behaviour of a compiler

With WebStorm, you can adjust the compiler by passing 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:

File watchers example of folder structure
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 store all the generated files in the output js folder

  1. In the Arguments field, type:

    --output $ProjectFileDir$\js\$FileDirRelativeToProjectRoot$\ --compile --map $FileName$

  2. In the Output paths to refresh field, type:

    $ProjectFileDir$\js\$FileDirRelativeToProjectRoot$\$FileNameWithoutExtension$.js:$ProjectFileDir$\js\$FileDirRelativeToProjectRoot$\$FileNameWithoutExtension$.map
    As a result, the project tree looks as follows:
    Example

Previewing compilation results without running a compiler

WebStorm 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. From 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.

Running CoffeeScript

There are two ways to run CoffeeScript in WebStorm:

  • Compile the CoffeeScript code manually and then run the output JavaScript code as if it were a Node.js application.

  • Run the original CoffeeScript code through the Node.js run configuration and have WebStorm compile it on the fly.

To compile CoffeeScript manually and run the generated JavaScript code

  1. Compile the CoffeeScript code into Javascript.

  2. Start creating a Node.js run configuration with the following mandatory settings:

    1. The Node.js engine to use. By default, the field shows the path to the interpreter specified on the Node.js page during Node.js configuration.

    2. In the Working directory field, specify the location of the files referenced from the starting CoffeeScript file to run, for example, includes. If this file does not reference any other files, just leave the field empty.field

    3. In the Path to Node App JS File field, specify the full path to the JavaScript file that was generated from the original CoffeeScript file during the compilation.

  3. Save the configuration and click the Run button on the toolbar.

  4. Proceed as while running a Node.js application.

To compile CoffeeScript on the fly during run

  1. This mode requires that the register.js file, which is a part of the 3 package, should be located inside the project. Therefore you need to install the coffee-script package on the Node.js page locally, as described in npm and Yarn.

  2. Open the starting CoffeeScript file in the editor or select in the Project tool window and choose Create <CoffecScript_file_name> from the context menunu. Alternatively, start creating a Node.js run configuration as described in To create a Node.js run/debug configuration. In the Run/Debug Configuration: Node.js dialog that opens, specify the following mandatory settings:

    1. The Node interpreter to use. Select the relevant interpreter configuration or create a new one, see By default, the field shows the path to the interpreter specified on the Node.js page during Node.js configuration.

      For Linux and macOS, this setting is overridden by the Node.js from the path to the CoffeeScript compiler executable file.

    2. In the Node parameters field, type --require coffee-script/register.

    3. In the Working directory field, specify the working directory of the application. By default, the field shows the project root folder.

    4. In the JavaScript file field, specify the full path to the CoffeeScript file to run.

    Note that all the mandatory fields will be filled in automatically if you create a run configuration directly from the required CoffeeScript file.

  3. Save the configuration and click the Run button on the toolbar.

  4. Proceed as while running a Node.js application.

Debugging CoffeeScript

To debug CoffeeScript in WebStorm, you need source maps generated in addition to the JavaScript code. Source maps set correspondence between lines in your CoffeeScript code and in the generated JavaScript code, otherwise your breakpoints will not be recognised and processed correctly. JavaScript and source maps are generated by compiling the CoffeeScript code manually using the File Watcher of the type CoffeeScript. After that you can debug the output JavaScript code as if it were a Node.js application.

Debugging CoffeeScript is supported only in the local mode. This means that WebStorm itself starts the Node.js engine and the target application according to a run configuration and gets full control over the session.

For more details about debugging Node.js applications, see Running and Debugging Node.js.

To debug CoffeeScript code

  1. Set the breakpoints in the CoffeeScript code where necessary.

  2. Compile the CoffeeScript code into Javascript using the File Watcher of the type CoffeeScript.

  3. Start creating a Node.js run configuration with the following mandatory settings:

    1. The Node.js engine to use. By default, the field shows the path to the interpreter specified on the Node.js page during Node.js configuration.

    2. In the Working directory field, specify the location of the files referenced from the starting CoffeeScript file to run, for example, includes. If this file does not reference any other files, just leave the field empty.

    3. In the Path to Node App JS File field, specify the full path to the JavaScript file that was generated from the original CoffeeScript file during the compilation.

  4. Save the configuration and click the Debug button on the toolbar.

  5. Proceed as while debugging a Node.js application locally.

Configuring syntax highlighting

You can configure CoffeeScript-aware syntax highlighting according to your preferences and habits.

  1. In the Settings/Preferences dialog (Ctrl+Alt+S), go to Editor | Color Scheme | CoffeeScript.

  2. Select the color scheme, accept the highlighting settings inherited from defaults or customize them as described in Configuring Colors and Fonts.

Last modified: 17 September 2019

See Also

Language and Framework-Specific Guidelines: