ESM only + move to webtestrunnner (#467)

* chore: remove karma

* chore: update esm.test.mjs to use chai

* chore: specify with extension whether tests are ESM or CJS

* mv fuzz.test to mjs, mv esm.test to chai.assert

* chore: move slug.test to ESM

* chore: move to ESM only

BREAKING CHANGE: This module only supports ESM. CommonJS and non-ESM
script tags are no longer supported.

* chore: add web-test-runner

* chore: add coverage reporting for CLI tests

* chore: fail CLI tests if coverage is not 100%

README.md

@@ -6,7 +6,7 @@ Make strings URL-safe.
 
 - Respects [RFC 3986](https://tools.ietf.org/html/rfc3986)
 - No dependencies
-- Works in browser (`window.slug`) and AMD/CommonJS-flavoured module loaders
+- Works in the browser or in Node.js
 
 ```
 npm install slug
@@ -21,7 +21,7 @@ npm install --save-dev @types/slug
 ## Example
 
 ```javascript
-var slug = require('slug')
+import slug from 'slug'
 var print = console.log.bind(console, '>')
 
 print(slug('i love unicode'))
@@ -114,16 +114,15 @@ slug.defaults.modes['pretty'] = {
 
 Here are some key differences between this package and [`slugify`](https://github.com/simov/slugify).
 
+- **Stability:** `slug` is ESM-only.  
+  `slugify` supports CommonJS and ESM.
 - **Defaults:** `slug` has the `lower` option enabled by default, lowercasing all slugs
   (`'On SALE'` becomes `'on-sale'`).  
   `slugify` has the `lower` option disabled by default (`'On SALE'` becomes `'On-SALE'`).
 - **Symbols:** `slug` removes unrecognized symbols (`'$100'` becomes `'100'`, `'<5'` becomes `'5'`, etc.).  
   `slugify` maps them to words (`'$100'` becomes `'dollar100'`, `'<5'` becomes `'less5'`, etc.).
 - **Empty Output:** `slug` will return a short, predictable hash (`'   '` becomes `'icag'` and `'🎉'` becomes `'8joiq'`).  
   `slugify` will return an empty string (`'   '` and `'🎉'` become `''`).
-- **Stability:** `slug` is planning [a new release](https://github.com/Trott/slug/blob/beta/CHANGELOG.md) that will drop support for CommonJS
-  and only support ESM modules.  
-  `slugify` will continue to support CommonJS and is likely to remain stable for the foreseeable future.
 
 ## Playground
 

benchmark/benchmark.js

@@ -1,4 +1,4 @@
-const slug = require('../slug')
+import slug from '../slug.js'
 
 const BENCHMARK_RUNS = 2048
 const MAX_WORD_LENGTH = 16

cli.js

@@ -1,6 +1,6 @@
 #!/usr/bin/env node
 
-const slug = require('./slug.js')
+import slug from './slug.js'
 
 if (process.argv.length < 3) {
   console.log('Usage: slug <string>')

index.html

@@ -42,7 +42,49 @@ <h1>Playground for slug module</h1>
 				</fieldset>
 			</form>
 		</main>
-		<script src="./slug.js"></script>
-    <script src="./playground.js"></script>
+    <script type="module">
+      import slug from './slug.js';
+
+			const form = document.getElementById('form')
+
+			form.addEventListener('submit', function (e) {
+				e.preventDefault()
+				if (form === null) {
+					console.error('form element not found')
+					return
+				}
+
+				const fd = new FormData(form)
+
+				const replacement = fd.get('replacement')
+				const lowercase = fd.get('lowercase')
+				const trim = fd.get('trim')
+				const fallback = fd.get('fallback')
+
+				const remove = fd.get('remove')
+				const regexG = fd.get('regex_g') === null ? '' : 'g'
+				const regexI = fd.get('regex_i') === null ? '' : 'i'
+
+				const opts = {}
+
+				if (replacement.length > 0) {
+					opts.replacement = replacement
+				}
+
+				if (remove !== null && remove.length > 0) {
+					const regex = new RegExp(`/${remove}/${regexG}${regexI}`)
+					opts.remove = regex
+				}
+
+				opts.lower = lowercase !== null
+
+				opts.trim = trim !== null
+
+				opts.fallback = fallback !== null
+
+				const output = slug(document.getElementById('input').value, opts)
+				document.getElementById('slugOutput').innerText = output
+			})
+	</script>
   </body>
 </html>