Also distribute CommonJS version of library

Author: dphilipson

.gitignore

@@ -6,4 +6,5 @@ node_modules
 yarn-debug.log
 yarn-error.log
 
+cjs
 dist

README.md

@@ -18,6 +18,7 @@ Status](https://travis-ci.org/dphilipson/transducist.svg?branch=master)](https:/
     -   [Using custom reductions](#using-custom-reductions)
     -   [Creating a standalone transducer](#creating-a-standalone-transducer)
 -   [Bundle Size and Tree Shaking](#bundle-size-and-tree-shaking)
+-   [ES Modules and Node](#es-modules-and-node)
 -   [Benchmarks](#benchmarks)
 -   [API](#api)
 
@@ -106,6 +107,9 @@ With NPM:
 npm install --save transducist
 ```
 
+If running in a Node environemnt, make sure to check the note [ES Modules and
+Node](#es-modules-and-node) below.
+
 This library, with the exception of the functions which relate to `Set` and
 `Map`, works fine on ES5 without any polyfills or transpilation, but its
 TypeScript definitions depend on ES6 definitions for the `Iterable` type. If you
@@ -272,6 +276,19 @@ For details, [see the tree shaking
 API](https://github.com/dphilipson/transducist/blob/master/docs/api.md#tree-shakeable-api)
 section of the API docs.
 
+## ES Modules and Node
+
+Transducist is distributed with ES module syntax (i.e. `import`/`export`, not
+`require()`) because doing so is required to take advantage of tree shaking. If
+you're running in a Node environment or your bundler is so old that it doesn't
+understand this syntax, you may encounter runtime errors complaining about
+unexpected tokens in `import` statements. To resolve this, use a CommonJS
+version of this library by importing from `transducist/cjs` instead:
+
+```ts
+const { chainFrom } = require("transducist/cjs");
+```
+
 ## Benchmarks
 
 [View the

package.json

@@ -5,6 +5,7 @@
     "main": "dist/index.js",
     "types": "dist/index",
     "files": [
+        "cjs/",
         "dist/"
     ],
     "sideEffects": false,
@@ -28,7 +29,7 @@
     "author": "David Philipson <david.philipson@gmail.com> (http://dphil.me)",
     "license": "MIT",
     "scripts": {
-        "build": "yarn run clean && tsc -p tsconfig.build.json && ./scripts/mark-classes-pure.sh",
+        "build": "yarn run clean && tsc -p tsconfig.build-es.json && tsc -p tsconfig.build-cjs.json && ./scripts/mark-classes-pure.sh",
         "clean": "rm -rf dist/*",
         "format-file": "prettier --write",
         "format": "git ls-files | egrep '\\.(js(on)?|md|scss|tsx?)?$' | xargs yarn run format-file",

scripts/mark-classes-pure.sh

@@ -8,4 +8,4 @@
 # Intentionally removes an extra space to keep the same length, to maintain
 # accuracy of sourcemaps.
 
-find dist | grep \.js$ | xargs perl -p -i -e 's~/\*\* \@class \*/ ~/\*\*\@__PURE__\*/~g'
+find {src,dist} | grep \.js$ | xargs perl -p -i -e 's~/\*\* \@class \*/ ~/\*\*\@__PURE__\*/~g'

tsconfig.build.json tsconfig.build-cjs.jsontsconfig.build.json renamed to tsconfig.build-cjs.json

@@ -3,7 +3,7 @@
         "declaration": true,
         "inlineSources": true,
         "noEmit": false,
-        "outDir": "dist",
+        "outDir": "cjs",
         "sourceMap": true
     },
     "exclude": ["__tests__/**/*"],

tsconfig.build-es.json

@@ -0,0 +1,8 @@
+{
+    "compilerOptions": {
+        "module": "es2015",
+        "outDir": "dist"
+    },
+    "exclude": ["__tests__/**/*"],
+    "extends": "./tsconfig.build-cjs.json"
+}

tsconfig.json

@@ -1,7 +1,7 @@
 {
     "compilerOptions": {
         "lib": ["es5", "es2015.iterable", "es2015.collection"],
-        "module": "es2015",
+        "module": "commonjs",
         "moduleResolution": "node",
         "noEmit": true,
         "noFallthroughCasesInSwitch": true,