3 files changed, 9 insertions, 12 deletions
diff --git a/ext/fetch/22_body.js b/ext/fetch/22_body.js
index b10540883..2d633ae39 100644
--- a/ext/fetch/22_body.js
+++ b/ext/fetch/22_body.js
@@ -37,7 +37,6 @@ import {
   readableStreamThrowIfErrored,
 } from "ext:deno_web/06_streams.js";
 const {
-  ArrayBufferPrototype,
   ArrayBufferIsView,
   ArrayPrototypeMap,
   DataViewPrototypeGetBuffer,
@@ -46,8 +45,6 @@ const {
   JSONParse,
   ObjectDefineProperties,
   ObjectPrototypeIsPrototypeOf,
-  // TODO(lucacasonato): add SharedArrayBuffer to primordials
-  // SharedArrayBufferPrototype
   TypedArrayPrototypeGetBuffer,
   TypedArrayPrototypeGetByteLength,
   TypedArrayPrototypeGetByteOffset,
@@ -56,6 +53,10 @@ const {
   TypeError,
   Uint8Array,
 } = primordials;
+const {
+  isAnyArrayBuffer,
+  isArrayBuffer,
+} = core;
 
 /**
  * @param {Uint8Array | string} chunk
@@ -412,7 +413,7 @@ function extractBody(object) {
       );
     }
     source = TypedArrayPrototypeSlice(object);
-  } else if (ObjectPrototypeIsPrototypeOf(ArrayBufferPrototype, object)) {
+  } else if (isArrayBuffer(object)) {
     source = TypedArrayPrototypeSlice(new Uint8Array(object));
   } else if (ObjectPrototypeIsPrototypeOf(FormDataPrototype, object)) {
     const res = formDataToBlob(object);
@@ -461,11 +462,7 @@ webidl.converters["BodyInit_DOMString"] = (V, prefix, context, opts) => {
     return webidl.converters["URLSearchParams"](V, prefix, context, opts);
   }
   if (typeof V === "object") {
-    if (
-      ObjectPrototypeIsPrototypeOf(ArrayBufferPrototype, V) ||
-      // deno-lint-ignore prefer-primordials
-      ObjectPrototypeIsPrototypeOf(SharedArrayBuffer.prototype, V)
-    ) {
+    if (isAnyArrayBuffer(V)) {
       return webidl.converters["ArrayBuffer"](V, prefix, context, opts);
     }
     if (ArrayBufferIsView(V)) {
diff --git a/ext/fetch/26_fetch.js b/ext/fetch/26_fetch.js
index 38605d5c9..b53013e49 100644
--- a/ext/fetch/26_fetch.js
+++ b/ext/fetch/26_fetch.js
@@ -51,7 +51,7 @@ const {
   StringPrototypeStartsWith,
   StringPrototypeToLowerCase,
   TypeError,
-  Uint8ArrayPrototype,
+  TypedArrayPrototypeGetSymbolToStringTag,
 } = primordials;
 
 const REQUEST_BODY_HEADER_NAMES = [
@@ -131,7 +131,7 @@ async function mainFetch(req, recursive, terminator) {
     const stream = req.body.streamOrStatic;
     const body = stream.body;
 
-    if (ObjectPrototypeIsPrototypeOf(Uint8ArrayPrototype, body)) {
+    if (TypedArrayPrototypeGetSymbolToStringTag(body) === "Uint8Array") {
       reqBody = body;
     } else if (typeof body === "string") {
       reqBody = core.encode(body);
diff --git a/ext/fetch/27_eventsource.js b/ext/fetch/27_eventsource.js
index a7f8ba77d..fa1d928e5 100644
--- a/ext/fetch/27_eventsource.js
+++ b/ext/fetch/27_eventsource.js
@@ -7,7 +7,7 @@ import { core, primordials } from "ext:core/mod.js";
 import * as webidl from "ext:deno_webidl/00_webidl.js";
 import { createFilteredInspectProxy } from "ext:deno_console/01_console.js";
 import { URL } from "ext:deno_url/00_url.js";
-import DOMException from "ext:deno_web/01_dom_exception.js";
+import { DOMException } from "ext:deno_web/01_dom_exception.js";
 import {
   defineEventHandler,
   EventTarget,