First working version with code extracted from Node.js 15

.babelrc.json

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+{
+  "presets": [],
+  "plugins": [
+    "@babel/plugin-proposal-class-properties"
+  ],
+  "env": {
+    "commonjs": {
+      "presets": [["@babel/preset-env", { "targets": { "node": "8" }, "modules": "commonjs" }]]
+    },
+    "esmBrowser": {
+      "presets": [["@babel/preset-env", { "modules": false }]]
+    },
+    "esmNode": {
+      "presets": [["@babel/preset-env", { "targets": { "node": "8" }, "modules": false }]]
+    }
+  }
+}

.eslintignore

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+coverage/

.eslintrc.json

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+{
+  "root": true,
+  "env": {
+    "browser": true,
+    "commonjs": true,
+    "es6": true,
+    "jest": true,
+    "node": true
+  },
+  "extends": ["eslint:recommended", "standard", "plugin:prettier/recommended"],
+  "globals": {
+    "msCrypto": true
+  },
+  "parser": "@babel/eslint-parser",
+  "rules": {
+    "no-var": ["error"]
+  }
+}

.gitignore

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+node_modules
+coverage/

.npmignore

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+__tests__/
+coverage/
+jsdom/
+.babelrc.json
+.eslint*
+.prettierrc
+*.tgz

.prettierrc

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+{
+  "arrowParens": "always",
+  "printWidth": 100,
+  "proseWrap": "never",
+  "singleQuote": true,
+  "trailingComma": "es5"
+}

README.md

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 # randomUUID
 
 Stub project for polyfilling `randomUUID` as proposed for standardization in
-https://github.com/WICG/uuid and implemented in Node.js v15.6.0
-https://github.com/nodejs/node/pull/36729
+Polyfill for the `crypto.randomUUID()` method as proposed in
+the [WICG randomUUID specification](https://github.com/WICG/uuid) and recently implemented in
+[Node.js v15.6.0](https://github.com/nodejs/node/pull/36729).
+
+## Usage
+
+Require module to polyfill `crypto.randomUUID()` method.
+
+```js
+require('randomuuid')
+```
+
+
+NOTE: ESM `import`able version not yet available.  See
+[this issue](https://github.com/uuidjs/randomUUID/issues/2) for status.
+## API
+
+See Node.js documentation for
+[randomUUID()](https://nodejs.org/dist/latest-v15.x/docs/api/crypto.html#crypto_crypto_randomuuid_options)
+for API usage.
+
+Note: The current implementation is based on Node.js `lib/internal/crypto/random.js`, however the intent of this project is to follow the spec, so node-specific details (such as the `disableEntropyCache` option) may or may not survive in future versions.

__tests__/polyfill.js

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+require('..');
+
+const { randomUUID } = typeof window === 'undefined' ? require('crypto') : window.crypto;
+
+test('Apply polyfill', function () {
+  // expect(randomUUID).toBeInstanceOf(Function)
+  expect(typeof randomUUID).toBe('function');
+});

__tests__/randomUUID.js

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+'use strict';
+
+const assert = require('assert');
+
+const randomUUID = require('../randomUUID');
+
+function testMatch(uuid) {
+  assert.match(uuid, /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/);
+}
+
+// Generate a number of UUID's to make sure we're not just generating the same
+// value over and over and to make sure the batching changes the random bytes.
+test('Generate multiple UUIDs', function () {
+  const last = new Set(['00000000-0000-0000-0000-000000000000']);
+
+  for (let n = 0; n < 130; n++) {
+    const uuid = randomUUID();
+    assert(!last.has(uuid));
+    last.add(uuid);
+    testMatch(uuid);
+
+    // Check that version 4 identifier was populated.
+    assert.strictEqual(uuid.substr(14, 1), '4');
+
+    // Check that clock_seq_hi_and_reserved was populated with reserved bits.
+    assert.match(uuid.substr(19, 1), /[89ab]/);
+  }
+});
+
+test("Test non-buffered UUID's", function () {
+  testMatch(randomUUID({ disableEntropyCache: true }));
+  testMatch(randomUUID({ disableEntropyCache: true }));
+  testMatch(randomUUID({ disableEntropyCache: true }));
+  testMatch(randomUUID({ disableEntropyCache: true }));
+
+  assert.throws(() => randomUUID(1), {
+    code: 'ERR_INVALID_ARG_TYPE',
+  });
+
+  assert.throws(() => randomUUID({ disableEntropyCache: '' }), {
+    code: 'ERR_INVALID_ARG_TYPE',
+  });
+});

browser.js

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+require('./polyfill')(window.crypto);

jsdom/jest.setup.js

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+const { randomFillSync: getRandomValues, webcrypto } = require('crypto');
+
+if (!window.crypto) window.crypto = webcrypto || { getRandomValues };

jsdom/resolver.js

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+const { sync } = require('browser-resolve');
+
+module.exports = sync;

node.js

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+const crypto = require('crypto');
+
+require('./polyfill')(crypto);
+
+let { webcrypto } = crypto;
+if (!webcrypto) crypto.webcrypto = webcrypto = {};
+
+if (!webcrypto.randomUUID) webcrypto.randomUUID = crypto.randomUUID;