Refactor code-style

*   Add more docs to JSDoc
*   Add support for `null` in input of API types

Author: wooorm

lib/index.js

@@ -4,7 +4,7 @@
  *
  * @typedef Options
  *   Configuration (optional).
- * @property {boolean} [dirty=false]
+ * @property {boolean | null | undefined} [dirty=false]
  *   Leave discouraged fields in the tree.
  */
 
@@ -14,12 +14,17 @@ import {visit} from 'estree-util-visit'
 const own = {}.hasOwnProperty
 
 /**
+ * Turn an estree into an esast.
+ *
  * @param {EstreeNode} estree
- * @param {Options} [options]
+ *   estree.
+ * @param {Options | null | undefined} [options]
+ *   Configuration (optional).
  * @returns {UnistNode}
+ *   esast.
  */
 export function fromEstree(estree, options = {}) {
-  /** @type {UnistNode|undefined} */
+  /** @type {UnistNode | undefined} */
   let tail
 
   visit(estree, {
@@ -29,7 +34,7 @@ export function fromEstree(estree, options = {}) {
       /** @type {EstreeNode} */
       // @ts-expect-error: indexable.
       const context = field === null || index === null ? parent : parent[field]
-      /** @type {string|number|null} */
+      /** @type {string | number | null} */
       const prop = index === null ? field : index
       /** @type {UnistNode} */
       const copy = {}
@@ -39,7 +44,7 @@ export function fromEstree(estree, options = {}) {
       for (key in node) {
         if (
           own.call(node, key) &&
-          (options.dirty ||
+          ((options && options.dirty) ||
             (key !== 'start' &&
               key !== 'end' &&
               key !== 'loc' &&
@@ -58,7 +63,7 @@ export function fromEstree(estree, options = {}) {
 
           // If this is a bigint or regex literal, reset value.
           if (
-            !options.dirty &&
+            (!options || !options.dirty) &&
             node.type === 'Literal' &&
             key === 'value' &&
             ('bigint' in node || 'regex' in node)