diff --git a/.gitignore b/.gitignore
index c977c85..15c4d8e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,6 @@
-.DS_Store
-*.d.ts
-*.log
 coverage/
 node_modules/
+*.d.ts
+*.log
+.DS_Store
 yarn.lock
diff --git a/build.js b/build.js
index 8f3fd94..3c91fa0 100644
--- a/build.js
+++ b/build.js
@@ -1,108 +1,94 @@
 import fs from 'node:fs'
 import https from 'node:https'
-import concat from 'concat-stream'
+import concatStream from 'concat-stream'
 import {bail} from 'bail'
 import {unified} from 'unified'
-import html from 'rehype-parse'
+import rehypeParse from 'rehype-parse'
 import {selectAll} from 'hast-util-select'
 import {toString} from 'hast-util-to-string'
 import {htmlElementAttributes} from './index.js'
 
-const processor = unified().use(html)
+const own = {}.hasOwnProperty
 
-// Global attributes.
-let globals = htmlElementAttributes['*']
+const processor = unified().use(rehypeParse)
 
-if (!globals) {
-  globals = []
-  htmlElementAttributes['*'] = globals
+if (!('*' in htmlElementAttributes)) {
+  htmlElementAttributes['*'] = []
 }
 
+// Global attributes.
+const globals = htmlElementAttributes['*']
+
 // Crawl WHATWG HTML.
-https.get('https://html.spec.whatwg.org/multipage/indices.html', onhtml)
-
-/**
- * @param {import('http').IncomingMessage} response
- */
-function onhtml(response) {
-  response.pipe(concat(onconcat)).on('error', bail)
-
-  /**
-   * @param {Buffer} buf
-   */
-  function onconcat(buf) {
-    const nodes = selectAll('#attributes-1 tbody tr', processor.parse(buf))
-    let index = -1
-    const result = {}
-    /** @type {string} */
-    let key
-    /** @type {string} */
-    let name
-    /** @type {string} */
-    let value
-    /** @type {string[]} */
-    let elements
-    /** @type {string} */
-    let tagName
-    /** @type {string[]} */
-    let attributes
-    /** @type {number} */
-    let offset
-
-    // Throw if we didn’t match, e.g., when the spec updates.
-    if (nodes.length === 0) {
-      throw new Error('Missing results in html')
-    }
-
-    while (++index < nodes.length) {
-      name = toString(nodes[index].children[0]).trim()
-      value = toString(nodes[index].children[1]).trim()
-
-      if (/custom elements/i.test(value)) {
-        continue
-      }
-
-      offset = -1
-      elements = /HTML elements/.test(value)
-        ? ['*']
-        : value.split(/;/g).map((d) => d.replace(/\([^)]+\)/g, '').trim())
-
-      while (++offset < elements.length) {
-        tagName = elements[offset].toLowerCase().trim()
-        attributes =
-          htmlElementAttributes[tagName] ||
-          (htmlElementAttributes[tagName] = [])
-
-        if (!attributes.includes(name)) {
-          attributes.push(name)
+https.get('https://html.spec.whatwg.org/multipage/indices.html', (response) => {
+  response
+    .pipe(
+      concatStream((buf) => {
+        const nodes = selectAll('#attributes-1 tbody tr', processor.parse(buf))
+        const result = {}
+        let index = -1
+
+        // Throw if we didn’t match, e.g., when the spec updates.
+        if (nodes.length === 0) {
+          throw new Error('Missing results in html')
+        }
+
+        while (++index < nodes.length) {
+          const name = toString(nodes[index].children[0]).trim()
+          const value = toString(nodes[index].children[1]).trim()
+
+          if (/custom elements/i.test(value)) {
+            continue
+          }
+
+          const elements = /HTML elements/.test(value)
+            ? ['*']
+            : value.split(/;/g).map((d) => d.replace(/\([^)]+\)/g, '').trim())
+          let offset = -1
+
+          while (++offset < elements.length) {
+            const tagName = elements[offset].toLowerCase().trim()
+
+            if (!own.call(htmlElementAttributes, tagName)) {
+              htmlElementAttributes[tagName] = []
+            }
+
+            /** @type {string[]} */
+            const attributes = htmlElementAttributes[tagName]
+
+            if (!attributes.includes(name)) {
+              attributes.push(name)
+            }
+          }
         }
-      }
-    }
 
-    const keys = Object.keys(htmlElementAttributes).sort()
-    index = -1
+        const keys = Object.keys(htmlElementAttributes).sort()
+        index = -1
+
+        while (++index < keys.length) {
+          const key = keys[index]
 
-    while (++index < keys.length) {
-      key = keys[index]
-      htmlElementAttributes[key].sort()
+          htmlElementAttributes[key].sort()
 
-      if (key !== '*') {
-        htmlElementAttributes[key] = htmlElementAttributes[key].filter(
-          (/** @type {string} */ d) => !globals.includes(d)
+          if (key !== '*') {
+            htmlElementAttributes[key] = htmlElementAttributes[key].filter(
+              (/** @type {string} */ d) => !globals.includes(d)
+            )
+          }
+
+          if (htmlElementAttributes[key].length > 0) {
+            result[key] = htmlElementAttributes[key]
+          }
+        }
+
+        fs.writeFile(
+          'index.js',
+          'export const htmlElementAttributes = ' +
+            JSON.stringify(result, null, 2) +
+            '\n',
+          bail
         )
-      }
-
-      if (htmlElementAttributes[key].length > 0) {
-        result[key] = htmlElementAttributes[key]
-      }
-    }
-
-    fs.writeFile(
-      'index.js',
-      'export const htmlElementAttributes = ' +
-        JSON.stringify(result, null, 2) +
-        '\n',
-      bail
+      })
     )
-  }
-}
+    .on('error', bail)
+})
diff --git a/test.js b/test.js
index fe6f718..454345b 100644
--- a/test.js
+++ b/test.js
@@ -21,23 +21,15 @@ test('htmlElementAttributes', function (t) {
   t.doesNotThrow(function () {
     /** @type {string} */
     let key
-    /** @type {string[]} */
-    let props
-    /** @type {number} */
-    let index
-    /** @type {string} */
-    let prop
-    /** @type {string} */
-    let label
 
     for (key in htmlElementAttributes) {
       if (own.call(htmlElementAttributes, key)) {
-        props = htmlElementAttributes[key]
-        index = -1
+        const props = htmlElementAttributes[key]
+        let index = -1
 
         while (++index < props.length) {
-          prop = props[index]
-          label = prop + ' in ' + key
+          const prop = props[index]
+          const label = prop + ' in ' + key
 
           assert.strictEqual(typeof prop, 'string', label + ' should be string')
           assert.strictEqual(