refactor: code review feedback

* include `void[]` as an options type
* create constant regex ahead of time
* document `defaultImageExtensions` in API section of readme
* add description to jsdoc/tsdoc options type

Co-authored-by: Titus Wormer <tituswormer@gmail.com>

index.js

@@ -2,17 +2,17 @@
  * @typedef {import('mdast').Root} Root
  * @typedef {import('mdast').Image} Image
  * @typedef {import('mdast').Link} Link
+ *
+ * @typedef Options
+ *   Configuration (optional).
+ * @property {Array<string>} [imageExtensions]
+ *   File extensions (without dot) to treat as images.
  */
 
 import isUrl from 'is-url'
 import {visitParents} from 'unist-util-visit-parents'
 import {is} from 'unist-util-is'
 
-/**
- * @typedef Options
- * @property {Array<string>} [imageExtensions] file extensions of images
- */
-
 const isImgPath = (/** @type {string} */ value) =>
   value.startsWith('/') || value.startsWith('./') || value.startsWith('../')
 
@@ -32,13 +32,13 @@ export const defaultImageExtensions = [
 /**
  * Plugin to add an improved image syntax.
  *
- * @type {import('unified').Plugin<[Options?], Root>}
+ * @type {import('unified').Plugin<[Options?]|void[], Root>}
  */
 export default function remarkImages({
   imageExtensions = defaultImageExtensions
 } = {}) {
-  const isImgExt = (/** @type {string} */ value) =>
-    new RegExp(`\\.(${imageExtensions.join('|')})$`).test(value)
+  const imgExtRegex = new RegExp(`\\.(${imageExtensions.join('|')})$`)
+  const isImgExt = (/** @type {string} */ value) => imgExtRegex.test(value)
 
   return (tree) => {
     visitParents(tree, 'text', (node, parents) => {

readme.md

@@ -85,12 +85,17 @@ Supported URLs / URIs:
 
 ##### `options`
 
-Configuration.
+Configuration (optional).
 
 ###### `options.imageExtensions`
 
 List of file extensions recognized as images (`Array.<string>?`, default
-`['svg', 'png', 'jpg', 'jpeg', 'gif', 'webp', 'avif']`).
+[`defaultImageExtensions`](#defaultimageextensions)).
+
+### `defaultImageExtensions`
+
+list of file extensions recognized as an image by default (constant `['svg', 'png', 'jpg', 'jpeg', 'gif', 'webp', 'avif']`).
+Note: extension does not include `.`, only the extension name.
 
 ## Security