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Rollup plugin for Fable (F# to JS compiler)


npm install --save-dev babel-core rollup rollup-plugin-fable


Create a rollup-config.js like the following:

import path from 'path';
import fableUtils from 'fable-utils';
import fable from 'rollup-plugin-fable';
import nodeResolve from 'rollup-plugin-node-resolve';
function resolve(relativePath) {
    return path.join(__dirname, relativePath);
var babelOptions = fableUtils.resolveBabelOptions({
  'presets': [
    ['es2015', {'modules': false}]
export default {
  entry: resolve('./my-app.fsproj'),
  dest: resolve('./dist/bundle.js'),
  plugins: [
    fable({ babel: babelOptions })
      // Other node-resolve options here
      // See
      customResolveOptions: {
          moduleDirectory: resolve('./node_modules')
  format: 'cjs'

Note we're resolving paths as well as Babel options and node modules to prevent conflicts in case Fable pulls files from outside the project local directory (for example, from Nuget cache).

Add this to your package.json.

  "rollup": "rollup -c rollup-config.js"

You can then bundle your app by running: dotnet fable npm-run rollup.

Check Fable website for more info

Normally you'll also install rollup-plugin-babel for other JavaScript files in your project (including those in Fable.Core) and you'll share the Babel options between both plugins. Check rollup-plugin-babel README and Babel website to find more info about the available options.

These are the options that can be passed to rollup-plugin-fable:

  • babel: Babel options as mentioned above.
  • define: Array of compiler directives passed to the F# compiler (like DEBUG). Note Fable will ignore the DefineConstants property in .fsproj.
  • plugins: Array of paths to Fable plugins (.dll files).
  • typedArrays: Translate numeric arrays as JS Typed Arrays. True by default.
  • clampByteArrays: If true, Fable will translate byte arrays as Uint8ClampedArray.
  • fableCore: Specify a directory containing Fable.Core JS files, normally used for testing new Fable versions.