Rework CJS output, add "module" to package.json

The build now produces `dist/esm` and `dist/cjs`, rather than `dist` and
`cjs`, and it specifies separate "module" and "main" fields in
`package.json` so that the correct type is chosen automatically.

Author: dphilipson

.gitignore

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

README.md

@@ -18,7 +18,6 @@ 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)
 
@@ -98,9 +97,6 @@ With NPM:
 npm install transducist
 ```
 
-If running in a Node environment, 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
@@ -267,20 +263,6 @@ 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`,
-instead of `require()`/`module.exports`) 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 the CommonJS version of this library instead by importing from
-`transducist/cjs`:
-
-```ts
-const { chainFrom } = require("transducist/cjs");
-```
-
 ## Benchmarks
 
 [View the

package.json

@@ -2,10 +2,10 @@
     "name": "transducist",
     "version": "1.0.2",
     "description": "Ergonomic JavaScript/TypeScript transducers for beginners and experts.",
-    "main": "dist/index.js",
-    "types": "dist/index",
+    "module": "dist/esm/index.js",
+    "main": "dist/cjs/index.js",
+    "types": "dist/esm/index.d.ts",
     "files": [
-        "cjs/",
         "dist/"
     ],
     "sideEffects": false,
@@ -29,8 +29,8 @@
     "author": "David Philipson <david.philipson@gmail.com> (http://dphil.me)",
     "license": "MIT",
     "scripts": {
-        "build": "yarn run clean && tsc -p tsconfig.build-es.json && tsc -p tsconfig.build-cjs.json && ./scripts/mark-classes-pure.sh",
-        "clean": "rm -rf cjs/* dist/*",
+        "build": "yarn run clean && tsc -p tsconfig.build-esm.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?)?$' | xargs yarn run format-file",
         "generate-toc": "git ls-files | egrep '\\.md$' | xargs scripts/markdown-toc-all.sh",

scripts/mark-classes-pure.sh

@@ -1,11 +1,11 @@
 #!/bin/sh
 
 # This replaces "/** @class */" with "/**@__PURE__*/" in all .js files in the
-# dist and cjs directories. This is useful because when TypeScript compiles
-# classes to ES5, it marks them with /** @class */, but UglifyJS looks for
-# /**@__PURE__*/ when performing dead code removal, such as during tree shaking.
+# dist directory. This is useful because when TypeScript compiles classes to
+# ES5, it marks them with /** @class */, but UglifyJS looks for /**@__PURE__*/
+# when performing dead code removal, such as during tree shaking.
 #
 # Intentionally removes an extra space to keep the same length, to maintain
 # accuracy of sourcemaps.
 
-find {cjs,dist} | grep '\.js$' | xargs perl -p -i -e 's~/\*\* \@class \*/ ~/\*\*\@__PURE__\*/~g'
+find dist | grep '\.js$' | xargs perl -p -i -e 's~/\*\* \@class \*/ ~/\*\*\@__PURE__\*/~g'

tsconfig.build-cjs.json

@@ -1,10 +1,7 @@
 {
     "compilerOptions": {
-        "declaration": true,
-        "inlineSources": true,
         "noEmit": false,
-        "outDir": "cjs",
-        "sourceMap": true
+        "outDir": "dist/cjs"
     },
     "exclude": ["__tests__/**/*"],
     "extends": "./tsconfig.json"

tsconfig.build-es.json

@@ -0,0 +1,11 @@
+{
+    "compilerOptions": {
+        "declaration": true,
+        "inlineSources": true,
+        "noEmit": false,
+        "outDir": "dist/esm",
+        "sourceMap": true
+    },
+    "exclude": ["__tests__/**/*"],
+    "extends": "./tsconfig.json"
+}