Use ESM

Author: wooorm

.gitignore

@@ -1,6 +1,5 @@
 *.log
 .DS_Store
-.nyc_output/
 coverage/
 node_modules/
 yarn.lock

.prettierignore

@@ -1,3 +1,2 @@
 coverage/
-*.json
 *.md

index.js

@@ -1,11 +1,9 @@
-'use strict'
+import {parse} from 'space-separated-tokens'
 
-var spaceSeparatedTokens = require('space-separated-tokens')
-
-module.exports = classnames
+var own = {}.hasOwnProperty
 
 // A bit inspired by <https://github.com/JedWatson/classnames>, but for hast.
-function classnames(node) {
+export function classnames(node) {
   var map = Object.create(null)
   var list = []
   var mutate = node && typeof node === 'object' && 'type' in node
@@ -42,7 +40,7 @@ function add(result, conditional) {
   if (typeof conditional === 'number') {
     result[conditional] = true
   } else if (typeof conditional === 'string') {
-    conditional = spaceSeparatedTokens.parse(conditional)
+    conditional = parse(conditional)
 
     while (++index < conditional.length) {
       result[conditional[index]] = true
@@ -54,7 +52,9 @@ function add(result, conditional) {
       }
     } else {
       for (key in conditional) {
-        result[key] = conditional[key]
+        if (own.call(conditional, key)) {
+          result[key] = conditional[key]
+        }
       }
     }
   }

package.json

@@ -24,34 +24,31 @@
   "contributors": [
     "Titus Wormer <[email protected]> (https://wooorm.com)"
   ],
+  "sideEffects": false,
+  "type": "module",
+  "main": "index.js",
   "files": [
     "index.js"
   ],
   "dependencies": {
-    "space-separated-tokens": "^1.0.0"
+    "space-separated-tokens": "^2.0.0"
   },
   "devDependencies": {
-    "hastscript": "^6.0.0",
-    "nyc": "^15.0.0",
+    "c8": "^7.0.0",
+    "hastscript": "^7.0.0",
     "prettier": "^2.0.0",
     "remark-cli": "^9.0.0",
     "remark-preset-wooorm": "^8.0.0",
     "tape": "^5.0.0",
-    "unist-builder": "^2.0.0",
-    "xo": "^0.38.0"
+    "unist-builder": "^3.0.0",
+    "xo": "^0.39.0"
   },
   "scripts": {
     "format": "remark . -qfo && prettier . -w --loglevel warn && xo --fix",
-    "test-api": "node test",
-    "test-coverage": "nyc --reporter lcov tape test.js",
+    "test-api": "node test.js",
+    "test-coverage": "c8 --check-coverage --branches 100 --functions 100 --lines 100 --statements 100 --reporter lcov node test.js",
     "test": "npm run format && npm run test-coverage"
   },
-  "nyc": {
-    "check-coverage": true,
-    "lines": 100,
-    "functions": 100,
-    "branches": 100
-  },
   "prettier": {
     "tabWidth": 2,
     "useTabs": false,
@@ -62,13 +59,10 @@
   },
   "xo": {
     "prettier": true,
-    "esnext": false,
     "rules": {
-      "guard-for-in": "off"
-    },
-    "ignores": [
-      "hast-util-classnames.js"
-    ]
+      "no-var": "off",
+      "prefer-arrow-callback": "off"
+    }
   },
   "remarkConfig": {
     "plugins": [

readme.md

@@ -12,6 +12,9 @@
 
 ## Install
 
+This package is [ESM only](https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c):
+Node 12+ is needed to use it and it must be `import`ed instead of `require`d.
+
 [npm][]:
 
 ```sh
@@ -21,8 +24,8 @@ npm install hast-util-classnames
 ## Use
 
 ```js
-var h = require('hastscript')
-var classnames = require('hast-util-classnames')
+import {h} from 'hastscript'
+import {classnames} from 'hast-util-classnames'
 
 console.log(classnames('alpha bravo', {bravo: false}, [123, 'charlie']))
 
@@ -44,6 +47,9 @@ Yields:
 
 ## API
 
+This package exports the following identifiers: `classnames`.
+There is no default export.
+
 ### `classnames(node, …conditionals)`
 
 Utility to merge classes.

test.js

@@ -1,9 +1,7 @@
-'use strict'
-
-var test = require('tape')
-var u = require('unist-builder')
-var h = require('hastscript')
-var classnames = require('.')
+import test from 'tape'
+import {u} from 'unist-builder'
+import {h} from 'hastscript'
+import {classnames} from './index.js'
 
 test('hast-util-classnames', function (t) {
   t.throws(