Use ESM

.gitignore

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

.prettierignore

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

index.js

@@ -1,27 +1,16 @@
-'use strict'
+import {stringify as commas} from 'comma-separated-tokens'
+import {stringify as spaces} from 'space-separated-tokens'
+import {html, svg, find} from 'property-information'
+import {position} from 'unist-util-position'
+import {webNamespaces} from 'web-namespaces'
+import {zwitch} from 'zwitch'
 
-module.exports = toXast
-
-var comma = require('comma-separated-tokens')
-var html = require('property-information/html')
-var svg = require('property-information/svg')
-var find = require('property-information/find')
-var space = require('space-separated-tokens')
-var position = require('unist-util-position')
-var namespaces = require('web-namespaces')
-var xtend = require('xtend')
-var zwitch = require('zwitch')
+var own = {}.hasOwnProperty
 
 var one = zwitch('type', {
-  handlers: {
-    root: root,
-    element: element,
-    text: text,
-    comment: comment,
-    doctype: doctype
-  },
-  invalid: invalid,
-  unknown: unknown
+  handlers: {root, element, text, comment, doctype},
+  invalid,
+  unknown
 })
 
 function invalid(value) {
@@ -32,7 +21,7 @@ function unknown(value) {
   throw new Error('Cannot transform node of type `' + value.type + '`')
 }
 
-function toXast(tree, options) {
+export function toXast(tree, options) {
   var space = typeof options === 'string' ? options : (options || {}).space
   return one(tree, {schema: space === 'svg' ? svg : html, ns: null})
 }
@@ -62,6 +51,7 @@ function doctype(node, config) {
   )
 }
 
+// eslint-disable-next-line complexity
 function element(node, parentConfig) {
   var props = node.properties || {}
   var schema = parentConfig.schema
@@ -71,31 +61,39 @@ function element(node, parentConfig) {
   var key
   var info
 
-  if (props.xmlns === namespaces.html) {
+  if (props.xmlns === webNamespaces.html) {
     schema = html
-  } else if (props.xmlns === namespaces.svg) {
+  } else if (props.xmlns === webNamespaces.svg) {
     schema = svg
   } else if (props.xmlns) {
     // We don’t support non-HTML, non-SVG namespaces, so stay in the same.
   } else if (schema === html && node.tagName === 'svg') {
     schema = svg
   }
 
-  config = xtend(parentConfig, {schema: schema, ns: namespaces[schema.space]})
+  config = Object.assign({}, parentConfig, {
+    schema,
+    ns: webNamespaces[schema.space]
+  })
 
   if (parentConfig.ns !== config.ns) {
     attributes.xmlns = config.ns
   }
 
   for (key in props) {
+    if (!own.call(props, key)) {
+      continue
+    }
+
     info = find(schema, key)
     value = props[key]
 
     // Ignore nullish, false, and `NaN` values, and falsey known booleans.
     if (
-      value == null ||
+      value === undefined ||
+      value === null ||
       value === false ||
-      value !== value ||
+      (typeof value === 'number' && Number.isNaN(value)) ||
       (!value && info.boolean)
     ) {
       continue
@@ -108,9 +106,7 @@ function element(node, parentConfig) {
     // Accept `array`.
     // Most props are space-separated.
     else if (typeof value === 'object' && 'length' in value) {
-      value = info.commaSeparated
-        ? comma.stringify(value)
-        : space.stringify(value)
+      value = info.commaSeparated ? commas(value) : spaces(value)
     }
     // Cast everything else to string.
     else if (typeof value !== 'string') {
@@ -120,11 +116,7 @@ function element(node, parentConfig) {
     attributes[info.attribute] = value
   }
 
-  return patch(
-    node,
-    {type: 'element', name: node.tagName, attributes: attributes},
-    config
-  )
+  return patch(node, {type: 'element', name: node.tagName, attributes}, config)
 }
 
 function patch(origin, node, config) {

package.json

@@ -25,41 +25,37 @@
   "contributors": [
     "Titus Wormer <tituswormer@gmail.com> (https://wooorm.com)"
   ],
+  "sideEffects": false,
+  "type": "module",
+  "main": "index.js",
   "files": [
     "index.js"
   ],
   "dependencies": {
-    "comma-separated-tokens": "^1.0.0",
-    "property-information": "^5.0.0",
-    "space-separated-tokens": "^1.0.0",
-    "unist-util-position": "^3.1.0",
-    "web-namespaces": "^1.0.0",
-    "xtend": "^4.0.0",
-    "zwitch": "^1.0.0"
+    "comma-separated-tokens": "^2.0.0",
+    "property-information": "^6.0.0",
+    "space-separated-tokens": "^2.0.0",
+    "unist-util-position": "^4.0.0",
+    "web-namespaces": "^2.0.0",
+    "zwitch": "^2.0.0"
   },
   "devDependencies": {
+    "c8": "^7.0.0",
     "hastscript": "^6.0.0",
-    "nyc": "^15.0.0",
     "prettier": "^2.0.0",
     "remark-cli": "^9.0.0",
     "remark-preset-wooorm": "^8.0.0",
     "tape": "^5.0.0",
-    "unist-builder": "^2.0.0",
+    "unist-builder": "^3.0.0",
     "xastscript": "^2.0.0",
-    "xo": "^0.38.0"
+    "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,
@@ -70,14 +66,9 @@
   },
   "xo": {
     "prettier": true,
-    "esnext": false,
     "rules": {
-      "eqeqeq": "off",
-      "guard-for-in": "off",
-      "no-eq-null": "off",
-      "no-self-compare": "off",
-      "unicorn/prefer-number-properties": "off",
-      "unicorn/prefer-includes": "off"
+      "no-var": "off",
+      "prefer-arrow-callback": "off"
     }
   },
   "remarkConfig": {

readme.md

@@ -13,6 +13,9 @@
 
 ## 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
@@ -32,11 +35,11 @@ Say we have an `example.html` file, that looks as follows:
 …and our script, `example.js`, looks as follows:
 
 ```js
-var fs = require('fs')
-var unified = require('unified')
-var parse = require('rehype-parse')
-var toXast = require('hast-util-to-xast')
-var toXml = require('xast-util-to-xml')
+import fs from 'fs'
+import unified from 'unified'
+import parse from 'rehype-parse'
+import {toXast} from 'hast-util-to-xast'
+import {toXml} from 'xast-util-to-xml'
 
 // Get the HTML syntax tree:
 var hast = unified()
@@ -60,6 +63,9 @@ Yields:
 
 ## API
 
+This package exports the following identifiers: `toXast`.
+There is no default export.
+
 ### `toXast(node[, space|options])`
 
 Transform the given **[hast][]** *[tree][]* to **[xast][]**.

test.js

@@ -1,12 +1,10 @@
-'use strict'
-
-var test = require('tape')
-var ns = require('web-namespaces')
-var u = require('unist-builder')
-var h = require('hastscript')
-var s = require('hastscript/svg')
-var x = require('xastscript')
-var toXast = require('.')
+import test from 'tape'
+import {webNamespaces as ns} from 'web-namespaces'
+import {u} from 'unist-builder'
+import h from 'hastscript'
+import s from 'hastscript/svg.js'
+import x from 'xastscript'
+import {toXast} from './index.js'
 
 test('toXast', function (t) {
   t.test('main', function (t) {
@@ -190,7 +188,7 @@ test('toXast', function (t) {
     )
 
     t.deepEqual(
-      toXast(u('element', {tagName: 'br', properties: {prop: NaN}}, [])),
+      toXast(u('element', {tagName: 'br', properties: {prop: Number.NaN}}, [])),
       x('br', {xmlns: ns.html}),
       'should support attribute values: `NaN`'
     )