SystemJS Traceur Plugin

Provides Traceur transpilation in the browser and in builds when using SystemJS 0.19.12+ and SystemJS Builder 0.15+.

Compatible with the the automatic Rollup optimizations in SystemJS Builder.

Usage

jspm

jspm install plugin-traceur

Then set transpiler: 'plugin-traceur' in the jspm.js config file.

Alternatively use jspm init -p to set up the plugin automatically.

SystemJS

As well as this plugin, Traceur and Traceur Runtime must be manually configured.

This plugin is available at npm install systemjs-plugin-traceur.

Traceur can be installed via npm install traceur or from GitHub at https://github.com/jmcriffey/bower-traceur and https://github.com/jmcriffey/bower-traceur-runtime.

The npm version contains traceur.js and traceur-runtime.js within the bin folder.

The plugin can be used in SystemJS with the following configuration:

SystemJS.config({
  map: {
    'plugin-traceur': 'path/to/systemjs-plugin-traceur/plugin-traceur.js',
    'traceur': 'path/to/traceur.js',
    'traceur-runtime': 'path/to/traceur-runtime.js'
  },
  meta: {
    'traceur': {
      format: 'global',
      exports: 'traceur'
    },
    'traceur-runtime': {
      format: 'global',
      exports: '$traceurRuntime'
    }
  },
  transpiler: 'plugin-traceur',
  transpilerRuntime: false
});

It is important to set the transpilerRuntime: false option so that Traceur doesn't interfere with the deprecated internal Traceur compilation layer of SystemJS.

The metadata above is necessary otherwise Traceur will not load property in SystemJS.

The plugin can also be configured as a loader through metadata in SystemJS.

Traceur Options

Traceur compilation options can be set via traceurOptions in SystemJS:

SystemJS.config({
  traceurOptions: {
    asyncFunctions: true
  }
});

The full list of configuration options can be found at https://github.com/google/traceur-compiler/blob/master/src/Options.js#L25.

Building and Bundling

Build support works with no further configuration through the standard jspm build and bundle commands.

To build with SystemJS builder, use the following build configuration:

builder.bundle('app.js', 'out-bundle.js'); // create a named bundle
builder.buildStatic('app.js', 'out-static.js', { format: 'cjs' }); // create a static optimized build

When using builder.buildStatic, the ES module structure will be preserved and Rollup optimizations will included automatically allowing for static dead code removal.

Because Traceur runtime is a global, it can't be included in the Rollup optimizations. It can be useful to entirely separate out the traceur-runtime dependency from the build and have it in its own bundle, for example via:

builder.buildStatic('app.js - traceur-runtime', 'out-static.js', { format: 'cjs' });

This way, the entire bundle runs through Rollup for a fully-optimized output.

LICENSE

MIT