feat(regexp/unstable): add replaceAllAsync

Author: lionel-rowe

regexp/deno.json

@@ -3,6 +3,7 @@
   "version": "1.0.1",
   "exports": {
     ".": "./mod.ts",
-    "./escape": "./escape.ts"
+    "./escape": "./escape.ts",
+    "./unstable-replace-all-async": "./unstable_replace_all_async.ts"
   }
 }

regexp/unstable_replace_all_async.ts

@@ -0,0 +1,48 @@
+// Copyright 2018-2026 the Deno authors. MIT license.
+// deno-lint-ignore-file no-explicit-any
+
+/**
+ * Asynchronously replaces all occurrences of a pattern in a string.
+ *
+ * @experimental **UNSTABLE**: New API, yet to be vetted.
+ *
+ * @param text - The original string.
+ * @param searchValue - The regular expression pattern to search for.
+ * @param replacer - An asynchronous function that returns the replacement string.
+ * @returns A promise that resolves to the modified string.
+ *
+ * @example
+ * ```ts ignore
+ * import { replaceAllAsync } from "@std/regexp/unstable-replace-all-async";
+ * import { assertEquals } from "@std/assert";
+ *
+ * const result = await replaceAllAsync(
+ *   "https://example.com/ and https://example.com/not-found!",
+ *   /https:\/\/([\w\-/.]+)/g,
+ *   async (match, address) => {
+ *     const { status } = await fetch(match, { method: "HEAD" });
+ *     return `${address} returned status ${status}`;
+ *   },
+ * );
+ *
+ * assertEquals(
+ *   result,
+ *   "example.com/ returned status 200 and example.com/not-found returned status 404!",
+ * );
+ * ```
+ */
+export async function replaceAllAsync(
+  text: string,
+  searchValue: RegExp | string,
+  replacer: (substring: string, ...args: any[]) => Promise<string> | string,
+) {
+  const promises: (Promise<string> | string)[] = [];
+
+  text.replaceAll(searchValue, (...args) => {
+    promises.push(replacer(...args));
+    return "";
+  });
+
+  const results = (await Promise.all(promises))[Symbol.iterator]();
+  return text.replaceAll(searchValue, () => results.next().value!);
+}

regexp/unstable_replace_all_async_test.ts

@@ -0,0 +1,30 @@
+// Copyright 2018-2026 the Deno authors. MIT license.
+
+import { replaceAllAsync } from "./unstable_replace_all_async.ts";
+import { assertEquals } from "@std/assert";
+import { stub } from "@std/testing/mock";
+
+Deno.test(replaceAllAsync.name, async () => {
+  using _ = stub(
+    globalThis,
+    "fetch",
+    (u) =>
+      Promise.resolve(
+        { status: String(u).includes("not-found") ? 404 : 200 } as Response,
+      ),
+  );
+
+  const result = await replaceAllAsync(
+    "https://example.com/ and https://example.com/not-found!",
+    /https:\/\/([\w\-/.]+)/g,
+    async (match, address) => {
+      const { status } = await fetch(match, { method: "HEAD" });
+      return `${address} returned status ${status}`;
+    },
+  );
+
+  assertEquals(
+    result,
+    "example.com/ returned status 200 and example.com/not-found returned status 404!",
+  );
+});